This story was excerpted from Ian Browne’s Red Sox Beat newsletter. To read the full newsletter, click here. And subscribe to get it regularly in your inbox.

BOSTON -- When it comes to the 2024 Red Sox, no player has taken a bigger leap than Tanner Houck.

He won the fifth starter job at the end of Spring Training and quickly transformed into the staff ace. In fact, Houck is now one of the best pitchers in the Major Leagues, with the standard and advanced stats to prove it.

With a 1.91 ERA and a 0.92 WHIP over 85 innings, Houck is not only in play to be an All-Star, but he figures to be a top candidate to start the Midsummer Classic for the American League on July 16 in Arlington.

As Houck gets set to make his 14th start of the season on Thursday night at Fenway Park opposite a veteran stud in Phillies right-hander Aaron Nola, this seemed like an appropriate time to measure the top factors that have led to his quantum leap in Houck’s age-28 season.

Health

When Houck arrived at Spring Training in 2023, it was barely mentioned that he was coming off back surgery. This is because he opened camp on the same schedule as all the healthy starters on the team. In truth, coming back from back surgery wasn’t seamless.

“I think first and foremost, [it’s about] just kind of getting a year out from the back surgery. Being 100 percent healthy to where the body can just move how it wants,” said Houck. “Not to say that I was struggling with it last year, but I had a few deficiencies in terms of a little bit of strength to the back leg, the driving leg, which causes the delivery to kind of get out of whack because you're not as stable on the back leg.”

Houck seemed close to finding his stride last year, only to get struck in the face by a liner by Kyle Higashioka on June 16. Diagnosed with a facial fracture, Houck didn’t pitch again until Aug. 22.

Pitch usage/effectiveness

Before this season, Houck was essentially a two-pitch pitcher, relying on his filthy slider and two-seamer. He mixed in his splitter against lefties, but it was a mediocre pitch.

A breakthrough occurred prior to this season when new pitching coach Andrew Bailey worked with him on changing the grip of his splitter.

“It’s not a traditional split with the two fingers,” said Houck. “That’s what I was doing the years prior. But ultimately, when I had my first meeting with Bails, he showed me [Giants pitcher] Logan Webb's changeup/splitter grip.”

Houck has already thrown 300 splitters in 13 starts this season, compared to 198 in his 21 starts last year.

In 2023, opponents hit .310 against the pitch with a .452 slugging percentage. This season, Houck -- while getting fewer whiffs on the splitter (40.4% last season, 26.3% in 2024) -- has held hitters to a .183 average and a .247 slugging percentage on the split.

The improved splitter has made his slider even more difficult to hit. That Houck slider is the most valuable pitch in run value of any pitch in MLB this season.

“I do believe the split is a game-changer,” said Red Sox manager Alex Cora. “He can throw it for a strike, he can expand with it. We all know he can throw 94, 95, but that combination, slider-split, is really good.

Elite percentiles

The Statcast metrics serve as proof that Houck’s tremendous start is no fluke.

Take a look at the following breakdown of ’23 Houck vs. ’24 Houck:

• Expected wOBA: .316 in ‘23 (47th percentile), .288 in ‘24 (74th percentile)
• Barrel rate: 6.6% in ‘23 (73rd percentile), 3.9% in 2024 (90th percentile)
• Walk rate: 8.9% in 2023 (42nd percentile), 4.5% in 2024 (91st percentile)
• Strikeout rate: 21.4% in 2023 (34th percentile), 25.0% in 2024 (68th percentile)

Mindset

Houck has always had a laid-back demeanor, particularly in interviews. Don’t take that to mean he isn’t highly driven. Behind the scenes, he yearned to get where he is now.

“Over the past few years, I’ve always been frustrated with my performances. I have always known that I can be better. I've always known I can do better,” said Houck. “I've always known that I had the ability to do it and it was just kind of putting it together. And it was really about navigating those first few years to get to this point.

“I know the work isn’t done and I’m still developing this cutter to be a really quality pitch. The splitter and the slider and the two-seamer can always get better. You can't get too complacent with where I'm at now, but it's fun to be out there every fifth day.”