The Angels used the money they saved by not signing Shohei Ohtani to acquire a flawed reliever:

Right-hander Robert Stephenson and the Los Angeles Angels are in agreement on a three-year, $33 million contract that includes a conditional option that could be triggered if Stephenson misses a particular amount of time due to an elbow injury, sources familiar with the deal told ESPN on Sunday night.

The contract, expected to be official once Stephenson completes a physical on Monday, landed the Angels the best reliever left on the market — one who parlayed an incredible second half of last season into a deal worth $11 million per year.

ESPN.com

Stephenson posted a 1.1 rWAR in 2023, but never reached one WAR in his previous seven seasons. In fact, he only pitched one other season with a positive WAR.

The Pirates traded Stephenson to the Rays in the middle of 2023. With Tampa Bay, his K per 9 went from 10.9 per 9 IP to 14.1. His walks dropped from 5.1 per 9 IP to 1.9. His BABIP went from .273 to .194. What changed?

It looks like the Rays helped Stephenson make two improvements. The batted ball data show that he did not induce an infield pop up with the Pirates, but 20% of his fly balls were infield popups with the Rays. That suggests he put more backspin on his fast ball to make it drop less that hitters expected. That means they were swinging under the pitch, missing it or popping it up on contact.

The pitch type data shows that he added a cut fastball, and reduced his slider usage dramatically. So batters were seeing a new pitch from Stephenson, and it was very effective. The emphasis on the cutter increased the effectiveness of the slider, as the slider now became a surprise pitch..

Note that the reduced use of the slider should reduce the strain on his elbow, which is how Zack Greinke stopped his elbow pain. He used the slider only as an out pitch when he absolutely needed a K.

So it appears the Angels are taking a reasonable gamble here. I doubt that Stephenson will pitch as well as he did in the second half of 2023. Batters did not have time to adjust to his new approach. His new pitch mixture is a better pitch mixture, so if he can be a one WAR pitcher in each of the next three seasons, the contract will be worth it. The Rays do a great job of getting the most out of their relievers. The Angels need to learn from Tampa Bay and keep Stephenson moving toward better pitch selection.

Note that this changed very little for LAnaheim overall for 2024. They need many more moves like this to become a winner.