Dunning and Lambert have been pitching primarily out of the bullpen. I don't know how long it will take for them to get stretched out to be able to go 4-5 innings for a start. Gonzalez appears to be the only option here.
And keep in mind, Dunning and Lambert both are coming back from TJ. That's also a big factor. I think we are fine in hiding one TJ comeback in the rotation with Rodon being #5 and able to skip him occasionally, Not sure you can have 2/5 of the rotation being under a "stress watch" due to TJ.
Lopez sucking this bad early is a really big deal.