Now that Ranger Suárez has finally returned to the Phillies ’ rotation, Taijuan Walker is going to the bullpen. Initially, he will occupy a long relief role.

But could he eventually emerge as a late-inning option?

“Maybe,” manager Rob Thomson said Sunday before a rainy series finale against the Diamondbacks at Citizens Bank Park. “I’ve seen guys go to the pen and everything ticks up. I mean, he’s throwing the ball pretty good.”

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Indeed, that’s where the Phillies face a dilemma.

Walker posted a 2.54 ERA in six starts while Suárez was working his way back from spring-training back stiffness. The Phillies put Walker on an offseason program designed to recover lost velocity. Sure enough, the average velocity on his four-seam fastball has risen to 92.3 mph from 91.5 mph last season.

Thomson said he does expect to revisit the idea of using a six-man rotation , maybe even later this month during a stretch of 19 games in 20 days. Aaron Nola has pitched more innings than any pitcher in baseball since 2017, with Zack Wheeler not far behind. The Phillies also want to be careful with Jesús Luzardo, who didn’t pitch beyond June 16 last season with the Marlins because of injuries.

So, Thomson and pitching coach Caleb Cotham must weigh the value of keeping Walker’s arm stretched out as a No. 6 starter with the possibility that he could help a bullpen that could use another high-leverage arm.

Thomson believes Walker is willing to take on either role.

“It’s not that he’s happy going to the bullpen,” Thomson said. “But I think, when it gets right down to it, he’ll be there.”

The Phillies lean on lefties José Alvarado and Matt Strahm in the late innings. Jordan Romano and Orion Kerkering — the top righty options — have struggled at various points in the season. The bullpen ranks 24th in the majors with a 4.71 ERA.

Maybe Walker could help.

“I think how you go about it is you think of him as sort of a long guy, and then, at some point, work him into back-to-backs and, if possible, three out of four,” Thomson said. “He’s so strong and he’s such an athlete that I think he’d transition well to it, to tell you the truth.”

Bryce goes boom

Bryce Harper went 13 games without a homer before his opposite-field shot to left field against Diamondbacks lefty Eduardo Rodríguez in the first inning.

Not that Thomson was concerned.

“There’s not a whole lot of slug there right now, but it’s going to be there,” Thomson said. “He’s really the last guy I worry about.”

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Thomson did give Harper “a half-day” off by using him as the designated hitter. Harper started at first base in the season’s first 33 games.

“Maybe in between the at-bats he can get some extra work and hone his swing a little bit,” Thomson said. “I don’t think he’s that far off. His expectations of himself are higher than anybody else. He knows how important he is to the ballclub and to the city and the franchise, and so he wears it. He really does. That’s who he is.”

With Harper as the DH, Kyle Schwarber made his second start of the season in left field. Weston Wilson started at first base in place of Harper. Schwarber and Wilson also homered in the Phillies’ 11-9 loss in 10 innings.

Extra bases

Nola said he felt better after pitching with tightness in the right side of his neck Saturday. Nola, who threw six scoreless innings, doesn’t expect the issue to impact his next start, scheduled for Friday night in Cleveland. ... Schwarber extended his career-best on-base streak to 40 consecutive games with a first-inning walk. It’s the longest active streak in baseball and the longest by a Phillies hitter since Odúbel Herrera’s 45-gamer in 2017-18. ... After a day off, Wheeler (2-1, 3.48 ERA) is slated to start the series opener against Rays righty Drew Rasmussen (1-2, 2.64) at 7:05 p.m. Tuesday in Tampa.