It’s been a strange year for close friends. Edwin Díaz, Josh Hader, Ryan Helsley, Emilio Pagan, Carlos Estévez and others are on the injured list. Jeff Hoffman he lost his job with the Blue Jays. Pete Fairbanksrecently returned from IL, has a 10.00 earned run average. Devin Williams again Andrés Muñoz had ERAs over 5.00. Bryan Abreufilling in for Hader, has an ERA over 8.00. The Cardinals, on the other hand, are getting good results from a guy who never made it to the majors before his 30th birthday.
Louis achieved Riley O’Brien in very little trading in November of 2023. At the time, O’Brien didn’t even have a 40-man roster spot with the Mariners. All 29 other clubs had passed on him by the time Seattle placed him on waivers in the summer of 2022. He was about to become a major league free agent, but the Cards saw enough of O’Brien to send the cash to Seattle to acquire him and put him on their 40-man roster so he couldn’t hit the open market.
The music record at that time was not much. An eighth-round pick of the Rays in 2017, O’Brien began his career as a starting pitcher. He was traded to the Reds in August 2020 for a left tackle Cody Reed. Cincinnati added O’Brien to the 40-man roster in November to avoid entering the Rule 5 draft. Things did not go well with the Reds. O’Brien made his major league debut in 2021 but posted a 4.55 ERA in Triple-A. He was designated for assignment in early 2022 and was sent to the Mariners for cash or a player to be called up later.
O’Brien was moved to a relief role in 2022, a switch that didn’t immediately bear fruit. He finished the year with a 7.03 ERA in 39 2/3 Triple-A innings. He appeared to turn the corner in 2023 when he threw 55 Triple-A innings with a 2.29 ERA in the Pacific Coast League. O’Brien struck out 37.7% of the batters he faced and struck out 57.1% of the balls in play. His 13.6% walk rate showed he was still working on his control, but the Cards were interesting enough to make that small trade and give up the 40th spot to him.
That didn’t work out right away. O’Brien struggled early in 2024 and missed most of the season. He managed to play eight major league games and 14 more in Triple-A. He entered 2025 with just 10 1/3 major league innings under his belt. He turned 30 in February of that year, just before the start of the season.
O’Brien finally broke into the majors last year, pitching 48 innings with a 2.06 ERA. He wasn’t really as good as the ERA would suggest, though. His 11.1% walk rate was very high and his 22.6% strikeout rate was only average. His 54.1% ground ball rate was good but he got a lot of help with a .252 batting average on balls in play and an 82.8% average. His 3.61 FIP and 3.82 SIERA suggested he was good but not as good as the ERA made it seem.
The Cardinals sent him to the minors a few times last year and burned out his final year. That situation could take the pitcher off the roster, but that won’t happen anytime soon with O’Brien. He took a close role in St. Louis, with a 2.70 ERA and 12 saves in 20 innings so far this year. While that ERA is higher than last year, the numbers under the hood look much better. His 29.5% strikeout rate, 2.6% walk rate and 62% ground ball rate are all huge improvements. His .320 BABIP this year actually leans a little on the unlucky side. His 2.06 FIP and 1.67 SIERA suggest he actually deserves better than his ERA.
The results are supported by a strong arsenal. O’Brien averaged 98.4 miles per hour with his sinker, a pitch he threw 59.2% of the time. The second most used pitch this year is a sweeper that clocks in at around 83.8 mph, though he also uses a 91.5 mph slider, giving hitters two different pitches to be aware of. There is also some change in the mix, although that has made up less than 1% of his contributions this year.
O’Brien’s success is a big reason why the Cardinals are playing over their heads right now. They have a 24-18 record despite the active diversity. They have scored 194 runs and allowed 193. A +1 run differential gives them an expected 21-21 loss, but they have gone 8-3 in one-run games and 5-1 in extra innings. In short, they played like a .500 team overall but got three more wins in close contests. O’Brien’s 12-save shutout and three shutout wins certainly played a role in reducing those numbers.
It puts the Cards in an interesting position this summer. They had planned for this season to be a testing year. They traded Sonny Gray, Wilson Contreras, Nolan Arenado again Brendan Donovan in reconstructing the movements. The plan was to spend 2026 allowing less established guys to accumulate more playing time, so the club could figure out who is the building block and who has trade value.
Maybe the Cardinals will get back on top and make things easier for the team. If not, it can lead to some difficult decisions. The front office probably doesn’t want to buy at the deadline as that would require taking away from the farm system, at a time when they are trying to build it. In fact, they probably want to make more sales, too Lars Nootbaar, JoJo Romero, Dustin May, Nolan Gorman again Alec Burleson to be some reasonable traders.
O’Brien will be a very interesting player to follow. On the other hand, he is not close to working for free. He entered this year with one year and 129 days of service time. He is still under the club for another four seasons after this one. He might be eligible for compensation this offseason as a Super Two guy, but still, four years of arb for what looks like a potential tight end is a nice thing to have. There is guilt in keeping him around.
On the other hand, the performance of the release is often variable. O’Brien is 31 years old and does not have a long record of major league success. He walked 11.6% of the batters he faced in his minor league career. He had a 13.1% walk rate in the big games coming into this season. He is now walking just 2.6% of opponents this year. Did he suddenly go from bad control to elite, or will this reverse?
There is also the ever-present concern about injury with a pitcher, especially one who throws nearly 100 mph. Most fastball pitchers deal with arm issues these days and O’Brien had that aforementioned flexor strain in 2024.
There are a lot of pieces in motion here, making O’Brien an interesting player to watch in the coming months. As mentioned above, many clubs have experienced negative results from their close associates. Shortcuts are always in demand at the appointed time and that demand will be even greater this year. It’s controversial that the Cards got the money while O’Brien put up good numbers. By the time they plan to compete for real in a few years, he’ll be in his mid-3 years of age and who knows what his condition will be like then?
Between now and the August 3 deadline, there are a number of options. O’Brien could continue to close games but he could also see his slippage or possibly injury. A team can continue to win games and stay in the race or fall back. Trade talks won’t be intense for a while but the Cardinals will have some interesting calls this summer.
Photo courtesy of Dennis Lee, Imagn Images
