Is Matt Carpenter's decline a case study for Nolan Arenado and the Cardinals?

The third baseman conundrum that the St. Louis Cardinals faced in 2019 was primarily a product of Matt Carpenter's back woes that season. Carpenter, 33 at the time, had been a perennial All Star for more than half a decade up to that point in his career. From 2012-2018, Carpenter's OPS+ never dropped below 112, and it averaged 130 across those 7 seasons. He was a 3-time All Star, a Silver Slugger, and an MVP candidate in 3 different seasons.

Carpenter's career began to tumble after 2018, however. The infielder began experiencing back pain in July of 2019, and his statistics that year are evidence of his decline. Carpenter slashed .226/.334/.392 in 2019 for an OPS+ of just 92. He was a below-replacement-level player both offensively and defensively for the first time in his career, and fans were clamoring for a change at the hot corner.

Rookie Tommy Edman was ascending in 2019, and talks began to heat up between the St. Louis Cardinals and Colorado Rockies for Nolan Arenado, but the organization opted to stick with its veteran infielder in 2020 once again.

All of that changed once again in 2021. After a taxing shortened season in 2020, the Cardinals swung a major trade for cornerstone third baseman Nolan Arenado. Arenado was entering his age-30 season in 2021, and he was undoubtedly the best third baseman in baseball at the time. After spending 8 years with the Rockies and having minimal postseason experience to show, Arenado was itching to have some playoff success in St. Louis.

His first season in St. Louis was a bit of a regression from his mean, but a 119 OPS+ paired with 34 home runs in 2021 were more than enough, especially when factoring in his Gold Glove defense.

Arenado's 2022 season was all the more spectacular. In 148 games (620 plate appearances), Arenado slashed .293/.358/.533 for an OPS+ of 151 and a grand total of 42 doubles, 30 home runs, and 103 RBIs. Arenado received his 10th consecutive Gold Glove, his 5th Silver Slugger award, and he finished 3rd in MVP voting behind Manny Machado and teammate/winner Paul Goldschmidt. Arenado's 2022 season was spectacular in all facets.

2023 was a bit of a different story. Arenado played in only 144 games due to, you guessed it, back injuries. Arenado, most known for his hard work and dedication to his craft, had enough by September. Oli Marmol said of his third baseman that "it got to the point where if he doesn't feel like he can continue to do that -- and he was super genuine when he came in -- and he was like, ‘Oli, I don't think I can keep doing it.’ That's meaningful coming from him because he's a guy that in no circumstances ever wants to come out.”

There are some stark similarities between Matt Carpenter's best year and his subsequent down years and Nolan Arenado's best season and his slow decline.

Both Matt Carpenter and Nolan Arenado had the best seasons of their careers when they were 32--2018 for Carpenter and 2022 for Arenado. Both players also experienced severe back issues paired with regression in the following seasons--2019 for Carpenter and 2023 for Arenado.

Marp was able to play out his contract with St. Louis through the 2021 season, but he was not able to return to the heights he experienced in 2018. Carpenter's OPS+ of just 63 in 2021 was a sad sight to see for a player who once carried an offense from 2012-2018.

Nolan Arenado is showing similar signs of regression that Carpenter showed in the late 2010s. I don't expect to see Nolan Arenado regress as dramatically as Matt Carpenter did from 2019-2021, but there are still signs that age and recurring injuries are beginning to catch up with Arenado.

Arenado's walk and strikeout rates are going in the wrong directions, his average exit velocity has dropped from 89 MPH in 2021 to just 85.6 MPH in 2024 (albeit in only 6 games played at the time of writing this), and both his whiff and chase rates are going in the wrong direction. Arenado has never been a fast player by any means, but his sprint speed has also dropped from 25.5 (22nd percentile) MPH in 2021 to 24.9 MPH last year (6th percentile).

The fact that both Matt Carpenter and Nolan Arenado experienced back issues and regression in their age-32 seasons is noteworthy. Arenado's on-field performance last year and this spring have given fans pause and worry. Carpenter's career is a fine case study to see what we may be in for as Nolan Arenado continues to play into his mid-30s.

Personally, I hope this isn't the case. Arenado is a sure-fire Hall of Famer. It would be sad to see his career fizzle out these next 3-4 years. Hopefully, Nolan can turn it around this year and give the Cardinal faithful something to cheer about.