Taijuan Walker embarks on a minor-league rehab road for the Phillies

ST. LOUIS — The clock on Taijuan Walker’s return to the Phillies’ starting rotation is about to begin.

Walker is scheduled to start Thursday night and throw 60 to 65 pitches for triple-A Lehigh Valley, manager Rob Thomson said Monday. The righty has been sidelined since the last weekend of spring training by a shoulder impingement, a pinching pain in his joint.

Thomson outlined a timeline in which the Phillies will increase Walker’s workload in 15-pitch increments over three or four starts during a minor-league assignment that can last for as many as 30 days.

It’s possible, then, that Walker could rejoin the Phillies’ rotation by the first week of May.

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Keep an eye on the radar readings during Walker’s tune-up starts.

Walker’s fastball sat in the low 90s in a spring-training start March 20 against the Orioles. He was shut down three days later after feeling soreness before a bullpen session. He simulated three innings of live batting practice Saturday in Washington and averaged “basically 90,” Thomson said.

“Chillier day in a sim game-type situation without a whole lot of adrenaline,” Thomson said. “So, I’m hoping that it goes up as we build.”

Walker’s velocity varied wildly during stretches last season. Overall, though, his fastball averaged 92.9 mph.

Right-hander Spencer Turnbull, Walker’s rotation stand-in, made his second start Monday night in the series opener against the Cardinals. Turnbull tossed five scoreless innings in his Phillies debut last week against the Reds.

The Phillies were already leaning to rolling with Johan Rojas in center field for the postseason last year, but a three-game series in St. Louis all but clinched it. Rojas went 5-for-9 with two doubles against the Cardinals.

As the Phillies returned to St. Louis, Rojas was 1-for-22 with six strikeouts and two walks, prompting two questions: Is his confidence taking a hit with only one infield hit? And how much longer can the Phillies stick with him?

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“He seems fine,” Thomson said. “But I know that you’re a young guy in the big leagues and you’ve got the numbers he’s got, it’s going to weigh on you to a certain degree. But he seems fine.”

About that second question: Thomson noted that Rojas isn’t chasing as many pitches out of the strike zone. But he isn’t making much contact at all, albeit in a small sample. Rojas’ whiff rate so far is 35.7%, up from 25.9% last season. He’s also swinging at fewer pitches (46.4%, down from 54.4%), which could signal that he’s more tentative at the plate.

“He’s doing a lot of, not chase, but swing-and-miss right now,” Thomson said. “He’s just cutting his swing off a little bit instead of staying through it and using the entire field.”

Cristopher Sánchez allowed two stolen bases in his first start last week against the Reds and three more Sunday in Washington. The Phillies allowed a total of five steals in both games, an ignominious feat that hadn’t been accomplished against them since Aug. 12, 2018.

So, when Sánchez goes through his next between-starts throwing session, it may look different.

Thomson said Sánchez might move from the bullpen to the regular mound. Or else he might incorporate pickoff throws in the outfield before heading into the bullpen.

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“Just to work on getting the ball out of his hand a little bit quicker,” Thomson said.

The Phillies held a meeting late last season to reinforce to their pitchers the importance of holding runners. J.T. Realmuto routinely has one of the best pop times of any catcher in the league, so paying slightly closer attention to runners could give him additional edge.

“Actually, we talked about it again before the last series,” Thomson said. “It’s something that we’re working on constantly.”

Orion Kerkering is scheduled to pitch Tuesday and Thursday for Lehigh Valley and could rejoin the Phillies on Saturday. The young reliever was slowed in spring training by the flu. ... For the second time through the rotation, Thomson matched up Turnbull with backup catcher Garrett Stubbs. Realmuto has caught the other four starters twice apiece. ... Zack Wheeler (0-1, 0.75 ERA) is scheduled to start Tuesday night against Sonny Gray, who will making his Cardinals debut.