Here's how Stephenson became a dominant reliever

MLB.com reporter Paul Casella is filling in for this edition of Rhett Bollinger’s Angels Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

On the surface, the Angels’ addition of right-handed reliever Robert Stephenson may not seem like a bullpen-altering splash.

After all, Stephenson -- who signed a three-year, $33 million deal -- is a soon-to-be 31-year-old right-hander with a 4.64 career ERA over eight big league seasons, all while playing for four teams.

But now, let’s zero in only on the current version of Stephenson. You know, the guy who posted a 2.35 ERA over 42 appearances following his June 2 trade to the Rays last season.

That success wasn’t just the result of a small sample size or a change of scenery. It came about as a result of a completely revamped approach from Stephenson.

The biggest change Stephenson made was altering the release point on his slider. It sounds simple, but it essentially turned the pitch into a completely new offering -- and an incredibly effective one at that.

By tweaking his mechanics, the pitch is considerably faster and has a much tighter break, essentially making it a cutter -- though Stephenson still refers to the pitch as his slider. Whatever it is, the new version averaged 88.7 mph, well above the previous 84.8 mph average on his slider.

That’s a pretty significant increase for what is by far Stephenson’s most-used pitch. He threw his “cutter” 71.6% of the time from July onward.

And regardless of whether Stephenson truly discarded his slider in favor of a cutter or simply tightened up a pitch that was already a cutter, it’s hard to argue with the results.

Opposing batters hit just .101 (8-for-79) with 42 strikeouts against Stephenson's cutter. He had a 59.9% whiff rate with the pitch -- a sizable jump from the 41.8% whiff rate he registered with his old slider.

“Just making a little adjustment on how I release [the slider] helped add some velo to it,” Stephenson said. “I think that helped a ton on just putting the pitch in the zone more often and getting more swing and miss on it. Moving forward, I feel like that’s sustainable because it’s a better version of that pitch.”

Relying heavily on that pitch, Stephenson went from posting a 5.14 ERA in his 18 outings with the Pirates to becoming one of the most dominant relievers in the game with the Rays.

Stephenson not only put up a 2.35 ERA over 42 appearances with Tampa Bay, but his strikeout numbers skyrocketed. His strikeout rate went from 28% with the Pirates to 43% with the Rays.

From July onwards, Stephenson struck out 45% of the batters he faced. Of the 380 pitchers who faced at least 100 batters during that span, nobody had a higher strikeout rate than Stephenson.

"One of the things you look for from a player, especially from a scouting standpoint and just tracking a player over the course of time, is improvement,” Angels general manager Perry Minasian said. “He went to Tampa last year and was one of the best, if not the best, reliever in baseball over those 40 innings.”

Armed with his elite newfound cutter, Stephenson will undoubtedly be one of the top high-leverage options in an Angels bullpen that ranked 26th with a 4.88 ERA last season. And while incumbent closer Carlos Estévez was a first-time All-Star last season, he stumbled to a 6.59 ERA in 27 second-half appearances after his remarkable 1.80 ERA in the first half.

“We had a hard time in the sixth, seventh, eighth inning,” Minasian said. “For us to win more games, and especially compete, we have to be better in those middle innings. Adding a Stephenson, you try to push as many guys as you can down the pecking order. Stephenson gives us another high-leverage guy where [manager Ron Washington] can use him where he wants to and more depth in the bullpen, which we felt like was needed."