PHILADELPHIA -- Phillies first baseman Bryce Harper is going to be a real thing this week at Citizens Bank Park.

Harper is likely to start at least one game against the Brewers at first base, Phillies manager Rob Thomson said Sunday morning. Thomson declined to say which game it will be, but the three-game series begins on Tuesday night. Harper’s move from DH to first base will have implications for the 26-man roster, the defense and how the front office operates before the Aug. 1 Trade Deadline.

Whenever Harper takes the field at first, it will mark his first time playing defense in an MLB game since April 16, 2022, in Miami, when he played eight innings in right field. Harper has previously played first base twice in his MLB career, once in 2018 and once in 2021, each time for just one batter.

The roster
Darick Hall joined the Phillies on July 2 because they needed more pop in the lineup. Hall filled that same role last season, when Harper missed a couple months because of a broken left thumb. Around the time the Phillies activated Harper from the injured list in August 2022, they optioned Hall to Triple-A Lehigh Valley because he would have almost no opportunities to play going forward.

Thomson said recently that there is a way for Hall to remain with the team once Harper moves to first, but the Phillies could also look for somebody with more defensive versatility. Someone like Triple-A outfielder Jake Cave or utility player Kody Clemens, who are both on the 40-man roster, or utility player Scott Kingery, who is not, could fit the description.

The defense
Kyle Schwarber is expected to see more time at DH, although Harper will not play first base every day -- at least not at the beginning. Schwarber ranks last in baseball with -15 Outs Above Average, according to Statcast. Thomson has a couple options to fill Schwarber’s spot in the outfield: he could move Brandon Marsh to left field and play Johan Rojas in center, giving the Phillies their best defensive outfield in years. Or he could try for more offense in left field, meaning Cave, who is batting .347 with a 1.118 OPS in 261 plate appearances with Lehigh Valley.

“It depends on the offense, really, who you have available,” Thomson said about that decision. “Because for me, defense is so important, because it’s constant and it’s usually pretty consistent. Whereas offense ebbs and flows so much. I see where you take a guy like Rojas, if he keeps his head above water, and there’s not this huge upgrade in offense, and keeping him because you’re going to eliminate runs just with him being on the field.”

If Schwarber, Trea Turner and Harper heat up offensively, the offense at the bottom of the lineup should not matter as much. With a Rojas-Marsh outfield, meanwhile, the benefits to the pitching staff could be huge.

The Trade Deadline
The equation changes again if the Phillies find a bat to play left field before the Trade Deadline. Hunter Renfroe and Cody Bellinger are among the corner outfielders who might be available.

Asked if Harper could still play right field at some point this year, Thomson said, “If anything, later in the season.”

So that’s still on the table?

“Yeah, it’s on the edge,” Thomson said.

First things first, though, meaning Harper at first base beginning this week.