MILWAUKEE -- The Phillies¡¯ new No. 5 starter is the old No. 5 starter.

Taijuan Walker will start Thursday night¡¯s series opener against the Mets at Citi Field, Phillies manager Rob Thomson said Monday before the series opener against the Brewers at American Family Field. It could be an NL East title-clinching opportunity for the Phillies, depending how their series goes in Milwaukee.

"I like the way he threw the ball the other day,¡± Thomson said, referring to Walker¡¯s three scoreless innings on Saturday against the Mets. ¡°I really do. He¡¯s the most veteran guy on the club, and with the work that he¡¯s put in and the improvements that he¡¯s made, I think he¡¯s deserved it.¡±

The Phillies bumped Walker to the bullpen more than two weeks ago, after he posted a 9.17 ERA in four starts following a return from the injured list. He had a 6.50 ERA in 14 starts overall. (The Phillies went 4-10 in those starts.) But Philadelphia tried three different pitchers in Walker¡¯s spot this month, and none of them worked out. Rookie right-hander Tyler Phillips allowed six runs in two-thirds of an inning on Sept. 3 in Toronto. The Phillies optioned Phillips to Triple-A, and promoted rookie right-hander Seth Johnson from Lehigh Valley to take his place. Johnson allowed nine runs in 2 1/3 innings on Sept. 8 in Miami.

The Phillies turned to left-hander Kolby Allard on Saturday. He allowed four runs (three earned runs) in three innings.

That¡¯s a combined 27.00 ERA in three starts from Phillips, Johnson and Allard.

So it is back to Walker, who had a 4.50 ERA in eight innings over three relief appearances since moving to the bullpen, allowing 10 hits, two walks and two home runs in those eight frames. He struck out two. He generated 13 swings-and-misses.

"He¡¯s getting a lot of soft contact," Thomson said.

Entering play Monday, the Mets have a .723 OPS against right-handers this season. They have a .771 OPS against left-handers.

Asked if he envisioned a scenario where Walker returned to the rotation this year, Thomson said, ¡°I don¡¯t think you never say never, but the way that the other guys were throwing the ball -- Allard and the reports we had on Johnson, the way Tyler Phillips was throwing -- I thought, well, we¡¯ll be OK.¡±

Walker could make one more start on Sept. 24 against the Cubs at Citizens Bank Park after Thursday's outing against the Mets.