This is a tough time of year for Webb, he often fades a bit or cools off a bit around this time of year.
He's a great pitcher of course, so he never has any bad numbers any way you slice them, but look at his month splits and game logs from years past, and you'll see hints of this.
And then look at his last few starts and you can see that the lights-out dominant Webb may be in for a bit of cooling right now.