The Philadelphia Phillies are set to start the clock on the return of pitcher Taijuan Walker to their starting rotation.

The Phillies announced to reporters on Monday that Walker would make his first rehab start on Thursday at Triple-A Lehigh Valley. He began the season on the 15-day injured list with a right shoulder impingement.

Walker threw three simulated innings during batting practice in Washington this weekend. Philadelphia was encouraged enough to schedule his rehab assignment.

Once he pitches on Thursday, his 30-day rehab clock starts. By then, the Phillies will have to make a decision on his status.

They have also set some parameters around his workload.

Per MLB.com, the expectation is that Walker will throw 60 pitches in his first start with the Iron Pigs. From there, he will escalate in 15-pitch increments until he reaches at least 100 pitches. Philadelphia wants him fully built up before he rejoins the team.

To accomplish that Walker will need at least four starts.

For now, the Phillies have had Spencer Turnbull in his spot in the rotation, along with Zack Wheeler, Aaron Nola, Ranger Suárez and Cristopher Sanchez. Turnbull is likely the odd starter out when Walker returns, unless they turn to a six-man rotation.

Walker is an 11-year veteran who played his first season in Philadelphia last year, as he went 15-6 with a 4.38 ERA in 31 starts. He struck out 138 and walked 71 in 172 2/3 innings, the last of which was a career-high for the 31-year-old.

Walker has also pitched for Seattle, Arizona and Toronto and has a career record of 69-56 with a 3.97 ERA.

The Phillies are on the road this week at St. Louis before they return home to start a four-game series with Pittsburgh on Thursday.