BALTIMORE -- Alex Cobb proved more than the health of his right groin when he hopped on the Oriole Park mound for his season debut Thursday afternoon. Over the course of the club’s 8-4 home opener loss to the Yankees, Cobb also flashed the possibility that his secret weapon might be back.

It’s hard to draw conclusions from one start, but the effectiveness of Cobb’s split changeup was particularly noticeable over his 5 2/3 strong innings Thursday, for the way it flummoxed the likes of Aaron Judge and Luke Voit and the frequency with which Cobb trusted the pitch. Re-finding the feel for the split-change was a focus of this spring for Cobb, who used to throw such a filthy one it had its own nickname: “The Thing.” But consistency has been tough to find since Cobb underwent Tommy John surgery in 2015.

“I really liked it when I executed it,” Cobb said. “There were times when it wasn’t executed very well, and I got hurt by it. My goal is to minimize those types of pitches, but the good ones I was really happy with.”

The one split that struck in Cobb’s craw was this flatty to Gleyber Torres, which the Yankees shortstop socked into the left field seats for his first of two home runs on the day. But most of the others were effective, Cobb garnering a 52.6 percent whiff rate with his split change, his highest single-game mark since July 2014.

Cobb's highest single-game whiff rate* on split-change, career

Min. 10 swings vs. split-change (111 games)

1. 69.6% -- 6/13/14 vs. Astros

2. 60.0% -- 5/10/13 vs. Padres

3. 58.3% -- 4/12/14 vs. Reds

4. 55.6% -- 7/9/14 vs. Royals

5. 52.6% -- 4/4/19 vs. Yankees (with BAL)

*Whiff rate: Misses / Total swings

That success lent Cobb to throw the pitch more often. He used 32 split-changes Thursday, throwing it 36.8 percent of the time, per Statcast. That eclipsed his usage in all but six of his 28 starts in 2018, when Cobb struggled to a 5-15 record and 4.90 ERA in his first season in Baltimore. According to Brooks Baseball, his splitter enjoyed, on average, over three inches more vertical drop that it did on average in 2018.

“I have to be happy with the amount of quality pitches I threw,” Cobb said. “A lot of times last year I felt like I was on the defense. I want to go out there and attack hitters more.”

Cobb was much better in the second half last year, in no small part due to a reemergence of his premier weapon. After not throwing it at all in 2016 and just 14.3 percent of the time in 2017, Cobb threw 19 percent splits over the first three months of last season. Then starting in July, the usage spiked -- to 31.4 percent across the entire second half, per Statcast. Along came a 2.56 ERA across his final 11 appearances, compared to a 6.41 mark over his first 17 starts.

Split-change usage by year:

2012: 33.7 percent

2013: 33.9 percent

2014: 38.3 percent

2015: Did not play due to injury

2016: 0 percent

2017: 14.3 percent

2018: 26.3 percent

Cobb's ERA by year:

2012: 4.03

2013: 2.76

2014: 2.87

2015: Did not play due to injury

2016: 8.59

2017: 3.66

2018: 4.90

Again, Thursday represented just one start, but also a step into that dominant direction.