We all know Mune has been horrendous for the past month. But I actually wanted to know why. The Slump August 19th, 2026 was Murakami's first MLB game where he didn't generate a single 3 true outcome. No strikeouts, no walks, and no homers. He put a ball in play every AB that day against the Cubs. And that apparently broke him. Because since August 19th, Murakami has only had 9 hits. That's unheard of for someone that plays everyday (and was batting 2nd in the lineup until recently). His slash line during that time: .096/.248/.170 in 113 PA. For comparison, in Drew Romo's last 114 PAs with the Sox, his slash line is: .129/.221/.198. So how did a guy who was hitting .234/.372/.545 in his first 393 PA turn into of one of the worst hitting catchers in baseball history? Let's dive into the theories. The Hamstring Injury I've seen a narrative where the hamstring injury caused the slide. I don't think that's true. Mune had about a 2 week stretch where he needed to get acclimated to major league pitching again after taking 6 weeks off. In his first 10 games back he hit .176/.364/.294 with no homers. From that point on until August 19th, he hit .241/.359/.609 with 9 home runs. He was basically back to what he was doing pre-injury. But let's say something did change. Maybe the injury changed his swing. Maybe the home run derby did. Whatever your theory is, let's set a baseline. Before injury: .240/.378/.560, 94.2 MPH EV, 15 degree launch angle, 73.3 MPH bat speed, 18 degree attack angle, 7.8 feet swing length, 35 degree swing path tilt, 0 degree attack direction. 10 games after injury: .176/.364./294, 91.9 MPH EV, 20 degree launch angle, 74.2 MPH bat speed, 19 degree attack angle, 7.7 feet swing length, 36 degree swing path tilt, 4 degree opp attack direction. After-injury hot streak (7/25-8/18): .241/.359/.609, 94.9 MPH EV, 19 degree launch angle, 70.6 MPH bat speed, 19 degree attack angle, 36 degree swing path tilt, 3 degree opp attack direction. What's interesting here is that he was actually swinging the bat harder during his first 10 games back post injury, but he wasn't hitting the ball anywhere near as hard. That's understandable since he probably had to get his legs under him after 6 week hamstring injury. During his post injury hot streak, what stood out the most was his lower bat speed, yet much higher exit velos. You would expect lower bat speed to generate lower exit velos and less power, but that wasn't the case during this stretch. What may have accounted for this is that his barrels/PA went up about 3.6% over his pre-injury numbers. So he might have made a change to swing less hard in order to get better bat control. When you swing as hard as Mune, you don't need to try to hit it to the moon every time to hit for power. What's notable here is the big increase in launch angle. Over a sample of about 150 PAs, things like that may change, but a 4-5 degree difference is very notable. The 1 degree rise in attack angle and swing tilt meant that he had a more uppercut swing during this stretch, which can attribute to the higher launch angle. But this is not always the case (as you will see later). Another thing to note is the change in attack direction. Attack direction basically determines whether you are late (opp) or early (pull) on a swing. You actually want to be at 0 degrees, which is what Mune was at pre-injury. Post-injury, he was late on his swings, meaning he was hitting the ball deeper in the zone. You don't want this if you're a power hitter like him with an extreme upper cut swing. Because you're basically eliminating the optimal time in the zone with your bat path. So while Mune did get back to his pre-injury production after his hamstring injury, there is a change to his swing profile. It's fairly minor, but the change in launch angle and attack direction are definitely worth noting. I think the fact that he got back to pre-injury production after the injury means that alone is not the reason for his slump. No True Outcomes I'm going to use the 8/19 date as a cut-off because it's kind of fitting that not striking out, walking, or homering for a single game would break a hitter like Mune. But it's also the start of a gigantic cold streak for him, where he would hit .085 with no homers over the next 71 PA. Over that stretch, these were his numbers: .085/.239/.102, 91.8 MPH EV, 16 degree launch angle, 73 MPH bat speed, 21 degree attack angle, 38 degree swing tilt, 1 degree pull attack direction. Now compare this to the 3 week period before it. His launch angle drops while he starts swinging harder. His swing is now at the extreme bound of upper cut for a ML hitter. A 2-3 degree change in swing tilt mid-season is almost unheard of. The rise in attack angle is also pretty significant for an in-season change. He is also swinging earlier, perhaps opening up too much to try and catch up to velocity inside. This would leave him more vulnerable to outside pitches though. Just from an anecdotal standpoint, I remember watching him during this time and thinking that he was simply popping up too many fly balls with extremely high launch angles. Homers he'd hit before were now deep fly balls that died at the warning track because they were simply hit too high. However, the data is telling us that he actually lowered his launch angle. That might have to do with him potentially rolling over on pitches from swinging early. On September 5th, Murakami finally hit his 30th homer on a towering fly ball with a near 50 degree launch angle that barely made it over the left field wall. So slump over, right? Nope, the next 2 weeks would be more or less the same. Except his launch angle has somehow dropped even lower. 9/5-9/15: .114/.286/.161, 93.1 MPH EV, 9 degree launch angle, 70 MPH bat speed, 19 degree attack angle, 37 degree swing tilt, 6 degree opp attack direction. So we've got a case of a power hitter trying to lift the ball more with a more upper cut swing, but it's actually resulting in a lower launch angle. He's also seemingly slowing down his swing more in recent weeks. I think the somewhat small sample could be the reason why you see the variance in bat speed, but it could also just be him tinkering with his swing to try and get right. The complete change in attack direction also means that he is now hitting the ball much deeper in the zone than before. If he looks late on outside fastballs, it's because he's got no chance to hit them with how late he is swinging. What can we conclude from this so far? I think ever since his cold streak started, Mune has been tinkering with his swing, mostly trying to gain more loft to lift the ball. In the process, it seems like it broke his swing. He's now uppercutting more than ever, but is somehow hitting the ball at a lower launch angle. You usually wouldn't expect that combination. He's also consistently changing his swing to cover up for one weakness or another. The pull attack angle indicates he wanted to try and cover velocity while the opposite attack angle more recently suggests he wants to cover the low and outside breaking stuff. League Adjustment Another popular theory about Mune's demise is that the league has figured him out. This one may actually have some legs. Prior to 8/18, this is how the league pitched Mune: By pitch type: 28.8% 4FB, 5.8% cutter, 2.9% split, 14.7% sinker, 26.2% slider, 7.7% curveball, 2.6% knuckle curve, 11.2% change up. Since then, this is how they're pitching him: By pitch type: 25.7% 4FB, 9.1% cutter, 3.4% split, 10.5% sinker, 37.3% slider, 2.5% curveball, 11.2 % change up. The general trend is that they've stopped throwing him high in the zone and have moved more to low and outside. They're throwing him less fastballs and way more stuff that moves. The jump in slider % is probably the most drastic one, with the cutter increase being 2nd. I'm thinking that's righties throwing more cutters inside to him as well as low and in sliders. I've also seen quite a few try to backdoor him with a slider/cutter/split/change low and outside, which is exactly where the hottest part of the heatmap is. So there's an approach change for sure by the opposition and it seems like it has worked. But is this because they're attacking Mune's weaknesses or is this because of his swing change? Here's Mune's zone profile by wOBA prior to 8/18: He was more or less dangerous anywhere in the zone unless you threw him high and in. Also look at his numbers in the outside and low zone, it's actually one of his hotter zones. I don't think that opponents would have gotten away with the outside and low approach to Mune prior to his slump and swing change. If you want a laugh, here is his zone profile since 8/18: It's no wonder the advanced scouting caught up and they throw the ball low and outside to him now. But then again, his entire strike zone is cold unless you throw middle/low. What Broke Mune? I'm not a hitting coach. I don't have a great grasp on swing physics or swing paths. So in reality, I don't actually know. But I think from digging around on Statcast for a few hours a few things became clear. 1. The injury may have not directly caused his slump, but the time off made him alter his swing and timing. Murakami eventually adjusted to the new swing and timing to still produce like he did pre-injury. 2. Sometime around mid August, he drastically altered his swing to be more uppercut while also swinging earlier. This would cause him to go into a huge slump. 3. Around this same time, teams adjust and start throwing him low and away off-speed pitches. 4. Mune is now stuck in a cycle of tinkering where he's either trying to cover velocity or the low and slow stuff that pitchers are now spamming. No adjustment has worked thus far. I think the good news that I got out of this is that I don't think Mune is incapable of getting out of this slump. The physical characteristics are all still there. He can still swing hard. He's still capable of hitting the ball hard. His swing and timing are just so jacked up that he can't do it right now. The way that pitchers are pitching him is because of the adjustments he made to his swing in August. I think his zone profile prior to the slump kind of proves that he can handle pitches in the strike zone when he's going right. But, because he's so out of it right now, pitchers will keep spamming what works until he proves he can hit it again. I just wouldn't expect that to happen anytime this season.
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