For months, Cardinals president of baseball operations John Mozeliak vowed that the best way for the club to fill its pitching deficiencies would likely be to identify some duplication on its roster and then make trades for the needed arms.

The Cardinals did just that on Friday, trading outfielder Tyler O'Neill to the Red Sox for MLB reliever Nick Robertson and Minor League pitching prospect Victor Santos. Robertson, 25, will be added to the Cardinals’ 40-manroster, while Santos, 23, will be assigned to a Minor League roster in the coming days.

TRADE DETAILS
Red Sox receive: OF Tyler O'Neill
Cardinals receive: RHP Nick Robertson, RHP Victor Santos

“As we look to add pitching depth, as well as address concerns on potential playing time in the outfield, we felt this deal worked well in addressing both of those issues,” Mozeliak said in a release. “We are excited to add Nick to our bullpen, and we feel Victor gives us added depth in our Minor League system.”

The addition of Robertson comes on the heels of the Cardinals signing free-agent starting pitchers Sonny Gray, Lance Lynn and Kyle Gibson in recent weeks to restock a staff that lagged badly in last season’s 71-91 finish. St. Louis also plucked two players away from the Red Sox in Wednesday’s Rule 5 Draft, nabbing MLB reliever Ryan Fernandez and Minor League infielder Johnfrank Salazar.

Mozeliak has said that the Cardinals are interested in adding a front-office advisor to analyze their staff, and former Red Sox executive Chaim Bloom has reportedly been in talks with St. Louis about a position on its staff. Mozeliak said at the Winter Meetings that no one -- including Bloom -- has been hired to fill the advisory position.   

Mozeliak also insisted that adding depth and swing-and-miss stuff to the bullpen would be the Cardinals’ next order of business, and he accomplished that feat on Friday by landing the 6-foot-6, 265-pound Robertson. The right-hander, who made his MLB debut with the Dodgers in 2023 before being traded to the Red Sox in July, struck out 26 batters in 22 1/3 innings in the Majors.

In addition to saving the estimated $5.4 million that O’Neill is owed in 2024 for his final year of arbitration eligibility, per Spotrac, St. Louis also gains some roster flexibility with Robertson. The hard-throwing right-hander still has two Minor League options, and that roster flexibility is something that the Cardinals covet from their big league relievers. 

Robertson was picked in the seventh round of the 2019 MLB Draft by the Dodgers out of James Madison University. Used primarily as a reliever throughout his professional career, he has fanned 231 batters over 184 2/3 innings in the Minors. This past season, while pitching in Triple-A, he struck out 58 hitters in 42 2/3 innings.

Santos, a native of the Dominican Republic, was signed as an international free agent by the Phillies in 2016. He was traded to the Red Sox in July 2021 and was a non-roster invitee to Boston’s Spring Training in 2023. The 6-foot-1, 222-pounder missed the 2023 season because of an arm injury, but he has posted a 3-0 record and a 2.96 ERA in seven games (five starts) in the Dominican Republic Winter League.

Mozeliak said during the Winter Meetings earlier in the week that the club was likely to trade O’Neill because it had decided to go forward with a starting outfield of Lars Nootbaar, Tommy Edman and Jordan Walker, with Dylan Carlson serving as the primary backup, in the 2024 season. Mozeliak said O’Neill’s wishes to be an everyday player -- which St. Louis also considered him to be -- would not have allowed the Cardinals to get him the regular at-bats he was hoping for next season.

The Cardinals debated whether to non-tender O’Neill, 28, prior to the Nov. 17 deadline, but they instead hung on to the outfielder in hopes of flipping him in a trade for an asset.

O’Neill gave the Cardinals great hope that they had found a future star in left field in 2021 when he showed off his rare blend of speed, power and defensive capabilities. He hit .286 with 34 home runs, 80 RBIs and an OPS+ of 148 while finishing eighth in the voting for the National League Most Valuable Player award. However, shoulder and hamstring injuries limited him to just 96 games in 2022 (.228 batting average with a 99 OPS+) and more injury issues saw him play just 72 games in 2023 (.231 with a 94 OPS+).

O’Neill made headlines on April 4 when he was benched after Cardinals manager Oliver Marmol referred to his hustle while rounding third base as “unacceptable.” Thinking he would likely be held up following a hard-hit ball to Braves right fielder Ronald Acuña Jr. on a rainy night in St. Louis, O’Neill had to speed back up after slowing at third and was easily thrown out at the plate after being waved home by third-base coach Ron “Pop” Warner.

The two sides put the rift aside, but tensions bubbled beneath the surface all season, according to a source familiar with the Cardinals. Later in the season, O’Neill missed 11 weeks with a back injury that first surfaced in late April. The left fielder, who said the pain was so intense that he struggled to hold his infant daughter, said he only got relief in his back after seeing Southern California-based back specialist, Dr. Robert Watkins, who administered an epidural and a series of cortisone shots.

O’Neill returned to the Cardinals on July 20, and the team passed on trade offers from other clubs at the end of the month in hopes that the outfielder could finish the season strong and improve his value. He was shut down for the season on Sept. 17 because of a right foot sprain.

Mozeliak recently admitted that trading a player as talented as O’Neill could be risky, especially after the Cards were forced to look on as Randy Arozarena and Adolis García blossomed after leaving the Redbirds via deals to the Rays and Rangers, respectively.

“Yeah, [O’Neill] will probably get MVP votes,” Mozeliak said with a sly grin. “There’s a saying, ‘If you don’t make mistakes [on trades], you’re probably not trying.’ Do we wish we batted 1.000 [on trades]? Of course, but we are human, and we do make mistakes.”