The Philadelphia Phillies have one too many infieldersfollowing Mondays acquisition of second baseman Luis Arrez from the San Francisco Giants. So Bryce Harpers moving back to a familiar spot. Manager Don Mattingly told reporters Monday that Harper will move from first base back to his former position in right field to make room for Arrez. Alec Bohm will move from third base to first, Bryson Stott will move from second base to third and Arrez will slot in at second base for his Phillies debut on Tuesday. Trea Turner, whos in the midst of the worst defensive campaign of his career, is the only Phillies infielder staying put. Hell remain at shortstop. Tommy John forced Harper from RF to 1BHarper, 33, played the first 11 seasons of his MLB career primarily in the outfield. He underwent offseason Tommy John surgery after the 2022 season and has played at first base or designated hitter since. Harpers throwing arm is apparently in good enough shape for him to move back to the outfield, and, per Mattingly, he volunteered to move back to right field to make room for Arrez. Mattingly credited Harpers willingness to change positions as key to the Arrez trade.Harp had already kind of talked we had to make sure Harp was serious about playing the outfield, Mattingly said. I think that was kind of the key to doing anything.Mattingly told reporters that Harper would ease back into the outfield. What that means in practice isnt clear. Trea Turner staying at SS despite strugglesPer Mattingly, there were zero conversations about moving Turner from his position at shortstop. Turners struggled in the field this season with 18 errors in 106 games, the second most in baseball as of Monday. Hes on pace to easily surpass his career high of 23 errors in a full season set in 2023, when he led MLB in errors. And hes gotten away with several botched plays that could have been ruled errors, most notably in a July 20 game against the Los Angeles Dodgers when only one of his four miscues in the field was ruled an error by the official scorer in Philadelphia. Fortunately for Turner and the Phillies that night, he made up for it at the plate with two home runs to lead Philadelphia to a 10-7 win.Turners track record doesnt suggest a turnaround on defense. Maybe the Phillies decided it was best to keep him where he is than have him struggle to learn a new position late in the season.