The Cardinals are trading outfielder Tyler O’Neill to the Red Sox, reports Jon Heyman of The New York Post. Sean McAdam of MassLive reports that the Cards will receive two prospects. Alex Speier of the Boston Globe reports that they are right-handers Nick Robertson and Victor Santos. It has been officially announced by both clubs.

O’Neill, 29 in June, has had a mercurial career but showed his tremendous ceiling as recently as 2021. He played 138 games that season, hitting 34 home runs. He struck out at a high 31.3% clip but hit .286/.352/.560 overall for a wRC+ of 143. He also received strong grades for his outfield defense and stole 15 bases. That all-around production led to a tally of 5.5 wins above replacement, per FanGraphs, whereas Baseball Reference had him at 6.1 WAR.

But the results since then have been less impressive, with injuries seeming to drag him down. In the past two seasons, O’Neill has hit the injured list due to a right shoulder impingement, a left hamstring strain, a lower back strain and a right foot sprain. He’s been able to get into just 168 games over those two campaigns, hitting 23 home runs and producing a batting line of .229/.310/.397. That amounts to a wRC+ of 98, indicating he’s been just a bit below league average.

It appeared that he had fallen out of favor in St. Louis over that time. In early 2023, he and manager Oli Marmol got in a bit of a spat, where the skipper publicly admonished O’Neill for a perceived lack of hustle. Though the outfielder pushed back on the idea that he wasn’t giving full effort and also seemed displeased with Marmol making the disagreement public.

As the Cardinals fell out of contention during the most recent season, it seemed as though O’Neill could have been traded at the deadline a few months ago, since he’s slated for free agency after 2024. But no deal materialized and he stuck with the club into the current offseason. In recent weeks, trade rumors surfaced and president of baseball operations John Mozeliak did little to quell them. “In the outfield, right now, if we were to play tomorrow it’d likely be [Lars Nootbaar], Tommy Edman and [Jordan Walker],” said Mozeliak during the Winter Meetings earlier this week. “Our fourth outfielder would be Dylan Carlson. … Tyler O’Neill is somebody that we are listening to on trades.”

But for the Red Sox, O’Neill makes plenty of sense. After they traded Alex Verdugo earlier this week, their outfield projects to have lefties Masataka Yoshida, Jarren Duran and Wilyer Abreu. The club also has righties Ceddanne Rafaela and Rob Refsnyder, but the former has just 28 games of experience while the latter is a platoon specialist. Chief baseball officer Craig Breslow recently spoke about how the club would like to add a right-handed hitter capable of playing center field, but that it wouldn’t be a need.

O’Neill does indeed hit from the right side and has played some center field, having logged 303 2/3 innings there over 40 games in his career. The defensive reviews are mixed but it’s hard to glean much in such a small sample.

He will likely not be Plan A in center anyhow. Per a report from Jen McCaffrey and Chad Jennings of The Athletic this week, the club considers Rafaela a viable center field option. Even if he were to struggle in his first extended stretch of play in the big leagues, Duran has spent plenty of time up the middle and Abreu has seen action there as well. But all told, he balances the mix and will be a low-cost upside play for the Sox.

As mentioned, O’Neill is slated for free agency after 2024. Per MLBTR contributor Matt Swartz, he’s projected for a salary of just $5.5MM next year before reaching the open market. If he gets back to his 2021 upside, he would be a bargain and could help the club return to contention or perhaps turn into a midseason trade chip if the Sox are out of the race. If he continues to struggle, he can yield playing time to Duran, Rafaela or Abreu, depending on who is performing well.

The Cardinals came into this offseason with a notable position player surplus. Mozeliak outlined the outfield situation, which also includes players like Alec Burleson and Richie Palacios. But they also have Nolan Arenado and Paul Goldschmidt on the infield corners. Up the middle, they have Masyn Winn, Nolan Gorman and Brendan Donovan as potential options.

It was thought that they would use this surplus to add their rotation, where they were looking to add three arms. But they rather quickly signed Sonny Gray, Lance Lynn and Kyle Gibson to bolster their starting group. That led to recent speculation that an eventual position player trade would return bullpen help or prospects.

Robertson, 25, was drafted by the Dodgers and added to that club’s 40-man roster earlier this year, but he was flipped to Boston as part of the Enrique Hernández trade from a few months ago. He has 22 1/3 innings of MLB experience between the two clubs with an earned run average of 6.04, though with more encouraging peripherals. He struck out 24.5% of batters faced while walking 8.5% and getting grounders at a 47.1% clip. His .397 batting average on balls in play and 57.5% strand rate were both on the unlucky side of average, leading to a 3.88 FIP and 3.76 SIERA.

He was even better in the minors, having tossed 42 2/3 Triple-A innings between the two clubs with a 3.16 ERA, 33.1% strikeout rate and 7.4% walk rate. He still has a couple of options, so the Cards don’t need to commit an active roster spot to him right away, but he’s already had some MLB experience and could potentially be part of their club in the coming season.

Santos, 23, has mostly been a starter in the minors but hasn’t ever really been a top prospect, though he has received plaudits for his command. He tossed 145 innings in 2023, split between Double-A and Triple-A with a 4.97 ERA. His 20.6% strikeout rate was a bit below average but his 5.6% was quite strong. He’ll provide the Cards with a bit of non-roster depth for their starting staff.