He has been considered elite ever since he put a foot on a major league mound, and has been just that for the most part: a top reliever.
However, his 2021 season hasn’t gone smoothly, to put it lightly.
If we look at his full-season numbers, they are actually not that bad: a 3.05 ERA in 38.1 innings is something that most relievers would dream of.
However, there are several red flags in his profile that suggest he may no longer be a reliable late-inning option.
Let’s start with some facts.
Jansen’s Decline Phase Started A While Ago
Jansen was a truly elite reliever from 2010 to 2017.
Over that span, the bulky fireballer never had an ERA over three and consistently finished between 2.0 and 3.0 Wins Above Replacement, or WAR, even surpassing the mark two times in 2016 (3.1) and 2017 (3.4).
His Fielding Independent Pitching, or FIP, was never over 2.40 over that timeframe.
Then 2018 came, and Jansen stopped being elite.
His decline started that year, and since 2018, he has never posted an ERA below 3.00.
His FIP has also been at least at 3.03 since that campaign.
Jansen consistently struck out over 13 batters per nine innings from 2010 to 2017.
The numbers has never been higher than the 12.21 he has in limited games last season.
Decline is part of the game, and age eventually catches up to all of us.
Ballplayers are not the exception to the rule.
Since 2018, Jansen hasn’t been elite, but still was a serviceable late-inning option for the Dodgers.
This year, however, that may be starting to change.
Analyzing His 2021 Season
His ERA may be 3.05, but other run prevention metrics think Jansen has been a little worse than that.
kenley jansen in 2021: 3.05 ERA 3.47 xERA 3.66 FIP 4.79 xFIP 4.56 SIERA
blake treinen in 2021: 2.50 ERA 2.27 xERA 2.84 FIP 3.16 xFIP 2.94 SIERA
— alex vesia enjoyer (@bellisburner) July 23, 2021
His FIP is 3.66, his expected ERA 3.47, and his expected FIP is 4.79.
The xFIP stat in particular thinks he has been getting lucky by allowing few homers in comparison to the large amount of fly balls in his profile.
The problem with Jansen is that his recent performance is very worrisome.
Over his last seven games, his ERA is a ghastly 12.71, a product of eight earned runs in 5.2 frames.
In those 5.2 innings, he has conceded 13 (!) hits and six walks, for a 3.35 WHIP.
If we expand the sample size, we have him with a mediocre 5.14 ERA in his last 15 games (1.79 WHIP) and a 3.21 ERA in his last 30 games, with a 1.39 WHIP.
He seems to be experiencing an in-season decline, which is not exactly ideal for the Dodgers as they chase the San Francisco Giants in the National League West.
Jansen may be fixable to some degree, but it appears that his days as a trusted high-leverage option are over.
He is 33 years old, so it’s not that crazy to conclude his decline phase already started.
In his last three games, he has allowed nine runs (eight earned) in just two innings of work, and fans are turning against him.
As Kenley Jansen walked off the mound, he was greeted with boos from the home crowd, something that has happened in previous seasons when he has struggled.👀#MLB #Dodgers #SFvsLAD pic.twitter.com/HEkztHiTqJ
— Going Deep With Matthew and Jeremy (@GDWMattnJeremy) July 22, 2021
That kind of production simply doesn’t fit in the late innings, and the Dodgers may be forced to go to the trade market in their search for alternatives.