OKLAHOMA CITY -- Texas Rangers right-hander Max Scherzer struck out five while retiring 12 of the 14 batters he faced Sunday in his long-delayed second rehab start for Triple-A Round Rock since offseason surgery for a herniated disk in his lower back.

Scherzer threw four scoreless innings, then exited the game after an eight-pitch walk that opened the fifth against Oklahoma City, an affiliate of the Los Angeles Dodgers. That was the only walk for the three-time Cy Young Award winner who turns 40 on July 27.

The right-hander threw 37 of 53 pitches for strikes. The only hit he gave up was a sharp two-out single.

Scherzer's first rehab start was 52 pitches for Round Rock on April 24, but the second start was pushed back because of right thumb soreness that team doctors later identified as a nerve issue that extended to his right triceps. He had back surgery in mid-December and hasn't pitched for the Rangers since last season's World Series.

After a 40-pitch BP session in Texas on Tuesday, Scherzer said that he has been dealing with the thumb issue for more than a year.

The Rangers acquired Scherzer from the New York Mets in a deadline trade last July after the pitcher agreed to opt in on the final year of his contract for this season at $43.3 million. New York is paying $30.83 million of that to Texas in twice-monthly installments.

After the trade, Scherzer was 4-2 with a 3.20 ERA in eight starts for Texas, the last in the regular season on Sept. 12 before being sidelined by a muscle strain in his shoulder. He returned to make two starts in the American League Championship Series, then started Game 3 of the World Series before exiting after three innings because of his back.

His 3,367 career strikeouts are the second most among active pitchers -- Justin Verlander has passed him with 48 this season for Houston to get to 3,390. Scherzer is also second to Verlander on the active lists with 214 wins and 448 games started.