Red Sox closer Kenley Jansen needs to adapt to pitching rule changes

Kenley Jansen Boston Red Sox Press Conference
Kenley Jansen Boston Red Sox Press Conference / Billie Weiss/Boston Red Sox/GettyImages

Kenley Jansen is making the transition to the American League for the first time following a dozen years with the Los Angeles Dodgers and one season with the Atlanta Braves. Settling into a new city and switching leagues comes with an adjustment period but these aren't the only changes that the new Boston Red Sox closer will face. MLB is implementing several changes this season, a couple of which will force Jansen to alter his approach on the mound.

According to ESPN's Jeff Passan, MLB plans to emphasize enforcement of the balk rule in 2023.

A balk is intended to prevent pitchers from deceiving runners on base. There are several ways that a pitcher could violate this rule with an illegal motion in their delivery, in which case the umpire can allow the runner(s) to advance one base. The balk is arguably baseball's most complicated rule. It's a judgment call that sometimes appears obvious but other times can be nearly unrecognizable to the casual viewer. Umpires have gradually become more lenient with what they will allow pitchers to do with their delivery. Last season, 122 balks were called, the fewest in a full season since 1973. That will change if umpires start cracking down on balks, forcing pitchers to adjust.

Red Sox closer Kenley Jansen needs to adjust his delivery

Passan's report calls out a few pitchers who would be prone to the enforcement of the balk rule, including Jansen. When Jansen works out of the stretch with runners on base, he comes to a set position and then twitches his hip and his front leg.

Cracking down on balks coincides with MLB implementing a pitch clock. The clock is supposed to stop once the pitcher lifts his leg out of the set position, at which point his delivery is expected to begin. Any flinching movement, such as Jansen's hip and leg twitch, could be called a balk.

The pitch clock is another change that impacts Jansen more than most. Jansen had the slowest delivery in the majors last season, ranking dead-last with a 31.4 Tempo and 25.4 seconds between pitches with runners on base, per Baseball Savant. He was among the three slowest pitchers with the bases empty, taking 19.6 seconds. Under the new rule, pitchers will be required to throw within 15 seconds of receiving the ball when the bases are empty and within 20 seconds with runners on base.

Jansen will need to speed up his delivery in order to avoid being penalized by the pitch clock rule. Eliminating the twitch in his delivery to prevent a balk isn't enough since the clock is supposed to stop once the pitcher moves from the set position.

According to's Ian Browne, Jansen plans to skip the early rounds of the World Baseball Classic to focus on the pitch clock. He recognizes that he's the slowest pitcher in the league and he's prepared to make any changes necessary to abide by the new rule. Jansen hopes to join the Netherlands if they reach the semifinals in the WBC.

He should have plenty of time in training camp to work on his revised delivery and might get an opportunity to showcase it in the competitive environment of the WBC. The question is whether or not Jansen can remain as effective with this approach. He's no longer a pitcher who can blow hitters away with a fastball in the mid-90s. Jansen abandoned the higher velocity of his four-seam fastball a few years ago. He now relies heavily on a sinker that sits at around 93 mph, along with his cutter and slider. Without elite velocity, Jansen needs to be craftier.

The twitch in his delivery helped mess with the hitter's timing at the plate. He'll need to eliminate that from his delivery if umpires plan to enforce the balk rule while simultaneously speeding up his delivery to satisfy the pitch clock. Jansen will need to find a new way to disrupt a hitter's timing and keep them off balance.

Baseball is a game of adjustments. We've seen Jansen reinvent himself before while remaining among the game's top closers. Now he'll need to do it again to ensure the Red Sox have a reliable arm protecting the ninth inning for their bullpen.