Should the Phillies replace Taijuan Walker with Spencer Turnbull? It’s complicated.

I’d like nothing more than to sit here and tell you that the Phillies should bench Taijuan Walker. That’s called an easy day at the office in my line of work. Pick a number, any number. Rabble, rabble. See you at the first tee.

Unfortunately, the Phillies shouldn’t bench Taijuan Walker. It is unfortunate for a couple of reasons. One, it is a much more difficult case to make. Two, it means continued exposure to outings like the one we witnessed on Monday.

The Phillies’ 8-4 loss to the Giants was pretty much the opposite of why they’d entered the day at 38-16. It wasn’t just the 3-0 hole that Walker dug them in the second inning. It was the nature of the digging: a leadoff walk, a deep fly ball that moved the runners, a two-run double to deep right field. Eight batters, 28 pitches, 11 balls. At least first pitch was early.

Walker’s first six starts make it impossible to ignore Spencer Turnbull lurking in the bullpen. The 31-year-old righty was an April revelation, posting a 1.67 ERA with 36 strikeouts and 10 walks in 32⅓ innings. The Phillies won five of Turnbull’s six starts before Walker returned from the injured list and bumped him to long man.

Walker’s line through six starts: 5.51 ERA, 25 strikeouts, 12 walks, 32⅔ innings.

Like I said, it’s a tough case to make. Winning baseball starts on the mound. That is where the rhythm is set. It manifests at the plate, and in the field. When Walker struggles, he does so in a way that knocks the whole game out of rhythm. Last year, only three pitchers in the majors ran up more 3-0 counts. Walker’s first-pitch strike percentage ranked 68th out of 100 qualified pitchers. His 0-2 percentage ranked 86th. There is no greater slog than watching an innings-eater who consumes them in nibbles.

Yet, the Phillies’ decision to go with Walker over Turnbull was grounded in logic. Nothing about that logic has changed. The only potential value that Walker offers to the Phillies is his ability to give them five or six innings every five or six days. The only way for the Phillies to realize that value is to keep giving him the ball every five or six days. It really is as simple as that.

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There is value in innings, whatever they may look like. It is why the Phillies deemed Walker worthy of a four-year, $72 million contract two offseasons ago. They weren’t expecting him to be an All-Star, or even a guy who starts a playoff game. He was a league-average pitcher who gave them league-average production (a 99 ERA+) in 172⅔ innings over 31 starts last season. It doesn’t have to be pretty to be worth something.

A good framework for decision-making is to look at potential best- and worst-case scenarios. Right now, the Phillies have six starting pitchers for five slots. They have a bullpen slot for the odd man out.

Best-case scenario: The guy they choose to be the fifth starter gives them everything they need out of a fifth starter, more so than the odd man out would have. Meanwhile, the odd man out gives them positive value out of the bullpen.

At the moment, the Phillies clearly aren’t in the best-case scenario. Walker has been worse than Turnbull was, and Turnbull has a 6.75 ERA since moving to the bullpen. But that isn’t the worst-case scenario.

Worst-case scenario: The Phillies move Walker to the bullpen only to end up needing him back in the rotation at a later date, at which point he comes back as a lesser starting pitcher than he would have been had he remained in the rotation.

The pertinent question: Which is more likely to occur, the best-case or worst-case scenario?

Is there a chance Turnbull would give you 20 more starts of production on par with his first six? Sure, but that would give him twice as many starts as he has had in all but one big league season. His only season of 12-plus starts came with the Tigers in 2019, when he was essentially the pitcher Walker was last season and has been throughout his career: 4.61 ERA, 103 ERA+, 148⅓ innings, 30 starts.

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Even if that does happen, what are the odds the top four pitchers in the rotation remain healthy all season? In other words, what are the odds that Walker remains out of the rotation?

Go back to last season.

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.

At this time last year, I would not have thought Walker capable of the stretch he put together between late May and August. I’m even more skeptical this year. His underlying metrics suggest a pitcher who is fundamentally a lesser version of his peak self. His average velocity is down 1.5 mph. His contact rate has jumped to a career-high 85.7%. His ground-ball rate is a worrisome 35.2%. But the sample size is still small.

Fact is, the best version of the Phillies is one in which their No. 5 starter spends the bulk of the rest of the regular season as some version of the starter Walker has been for the bulk of his career, and in which they have a replacement starter waiting for a chance to prove himself in case of injury or abject implosion. At this point, the logical pecking order remains clear.

Nobody says you must enjoy it.