For the second time in four seasons, Ronald Acuña Jr., one of baseball's most dynamic players and the reigning National League MVP, will undergo season-ending reconstructive knee surgery.

Acuña suffered a torn left anterior cruciate ligament Sunday when he twisted awkwardly while changing directions on the basepaths, the Atlanta Braves announced after a review of MRI results.

Acuña, 26, told reporters he didn't believe he'd torn his ACL during the baserunning mishap in the first inning against the Pittsburgh Pirates. Acuña would know: In July 2021, he was on his way to an MVP season when he tore his right ACL, ending his season.

The Braves would backfill his position by acquiring three outfielders before the trade deadline and went on to win the 2021 World Series. Acuña climbed the victory platform that night in Houston but could only spectate, and he still wasn't fully recovered when he returned in 2022.

Last year, though, it all came together for one of the game's ultimate five-tool talents. Acuña put up an unprecedented 41-homer, 73-steal season — taking advantage of liberal rule changes for basestealers — and led the major leagues in on-base percentage (.416) and hits (212) and the NL in OPS (1.012).

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But after leading off the game with a double on Sunday, Acuña feinted toward third as if he might attempt a delayed steal, then twisted and tried returning to second. He sprawled on the infield dirt at PNC Park and was tagged out by Pirates starter Martín Pérez.

Results of the MRI confirmed the Braves' worst suspicions.

Acuña's injury is the second huge season-ending blow for the six-time NL East champions. Ace Spencer Strider underwent reconstructive Tommy John surgery on his elbow and will miss most of next season, too.

Acuña should return before Strider in 2025 - but it's no less bitter a blow for a club that once again has World Series aspirations.