Cardinals' recent roster move makes Tyler O'Neill trade look even worse

On Sunday morning, the St. Louis Cardinals made a roster move that is larger than it appears on the surface. Relief pitcher Riley O'Brien, who has been injured all season, was activated off the 60-day Injured List. In order to make space for the right-handed reliever, Nick Robertson was designated for assignment.

O'Brien was optioned to Triple-A Memphis where he will continue to display the potential that he has. According to Jeff Jones of the Belleville News-Democrat, the Cardinals want to see consistent success out of the righty since he's been injured all season; the organization is opting to stay with Kyle Leahy in the bullpen due to Leahy's success at the majors this year and him being more of a known quantity.

What makes this transaction all the more important is where Nick Robertson came from. Robertson was half of the returning package for oft-injured outfielder Tyler O'Neill from the Boston Red Sox this past offseason. Robertson, along with Victor Santos, were the two prospects the Cardinals received for the former MVP candidate.

While Tyler O'Neill has been having another strong offensive season, albeit with his usual splattering of injuries, the Cardinals have seen essentially no output from the players they received in exchange. Robertson, 26, made eight appearances with the Cardinals this year, and he had a 4.38 ERA in just 12.1 innings. His Triple-A numbers were significantly worse, however. He had a 7.48 ERA in 21.2 innings for Memphis this year.

Meanwhile, Victor Santos has been just as bad as Robertson at Triple-A. Santos has a 6.11 ERA to go along with a 1.583 WHIP in 66.1 innings this year. Now, the two players the Cardinals received for Tyler O'Neill are either out of the organization or pitching very poorly at the highest level of the minors.

Though Tyler O'Neill is once again on the Injured List, he's been a welcome surprise for the Boston Red Sox. In 298 at-bats, O'Neill has a .268/.357/.544 slash line and a 144 OPS+. He's hit 22 home runs -- a figure that would lead the Cardinals right now -- and driven in 45 batters. He's also accumulated 2.3 bWAR in about 75% of the appearances of players like Paul Goldschmidt, Brendan Donovan, and Nolan Arenado.

Both Tyler O'Neill and the Cardinals needed to part ways, but the return for a former MVP candidate who was returning to health after a rough couple of years felt light at the time. Just eight months later, and that hypothesis has turned out to be accurate.