I was going off of David Murphy's cherry-pick, which is still reasonable (perhaps even more so than month splits) even as a cherry-pick.
Walker’s first nine starts of 2023: 41⅓ innings, 6.53 ERA, 39 strikeouts, 19 walks, eight home runs. Phillies record: 5-4.
Walker’s next 17 starts of 2023: 101 innings, 3.03 ERA, 80 strikeouts, 40 walks, nine home runs. Phillies’ record: 14-3.
But either way, the body of work is undeniable: the wins, the innings and the WAR actually made him the #3 starter they wanted him to be, even if he is plainly not that now and it was only due to Suarez's injury and Nola's down year. And the career track record.
Versus Turnbull who had a 7.26 ERA last year, has only pitched 81 innings combined in the last three seasons, and was no better than Walker when he did pitch more in 2019-2020.