I looked over Hendriks' pitch selection and he's throwing fastballs to lefties 86% of the time. It was 72% last year and 68% in 2019.
His slider usage in general has gone down almost 10%. His curveball also hasn't gotten as many whiffs as it has in the past, but that could just be due to the small sample size so far, as he's mostly fastball/slider.
Out of the 18 sliders he's thrown, only 6 have been in the zone. Maybe 8 are considered pitches that a hitter can actually hit. A lot of them are waste/wipe out pitches. But most importantly, he's only thrown 3 sliders and 4 curveballs to left handed hitters. He threw 22% sliders to lefties last year and 7% curveballs. At least make the lefties worry about your off-speed pitch. I don't care if you throw 99, eventually guys are going to start cheating on the fastball. Today's game proves just that. There's no way Calhoun gets anywhere close to hitting that ball unless he knows a fastball is coming.
Unless Liam can no longer throw off-speed pitches for strikes, he should be fine. But I think this issue is very fixable.