Setup pitcher Brandon Morrow an X-factor for Dodgers in World Series

Los Angeles Dodgers relief pitcher Brandon Morrow (17) pitches in the eighth inning of Game 1 of the World Series at Dodger Stadium on Tuesday, Oct. 24, 2017, in Los Angeles. ( Brett Coomer / Houston Chronicle )
In the Astros' 7-6 comeback win over the Dodgers in Game 2, a double by Alex Bregman to lead off the eighth inning catalyzed the improbable blown save by Kenley Jansen, five home runs exchanged between the teams and the 11-inning war that split the series.But Bregman's hit required someone throw the pitch first. In that regard, Dodgers reliever Brandon Morrow bears responsibility for the ensuing epic.

In addition to igniting the Dodgers' meltdown, Morrow cost the bullpen its streak of 28 scoreless innings.

His mistake to Bregman is the worst blemish during his otherwise remarkable resurgence with the Dodgers this season. The 33-year-old former top prospect and starter turned into an elite setup man.

The Dodgers called him up from Class AAA Oklahoma City at the end of May. He exploded out of the bullpen with 100-mph fastballs, 92-mph cutters and 89-mph sliders.

"From the first hitter he faced, everybody turned their heads in the dugout and looked at each other and we're like, 'Okay, there's our set-up guy,'" said Dodgers starter Alex Wood, whose stint on the disabled list allowed for Morrow's promotion.is 12th year of professional baseball, his first healthy season in years, Morrow compiled a 2.06 ERA, with 50 strikeouts in 43 2/3 innings. The righthander held hitters to a .194 batting average.

"He's been monumental for our bullpen and for our team," Wood said. "It's a lot of fun to watch, too, seeing a 100 (mph fastball), with that slider at 92. It's pretty special."

Morrow was special from the start. In the 2006 draft, the Mariners selected Morrow fifth overall, ahead of pitchers Andrew Miller, Clayton Kershaw and Max Scherzer. The Mariners brought him to the majors a year later as a closer and then inserted him into the starting rotation.

He was a middling starter. He totaled a 4.32 ERA in 644 1/3 innings. He peaked with 17 strikeouts in a one-hit shutout against the Rays in 2010.

High walk rates beset and a myriad of injuries interrupted his first decade in the majors: biceps tendinitis in 2009, a strained rib cage in 2012, a nerve problem in his forearm in 2013, a torn tendon in his index finger in 2014, surgery to remove damaged tissue from his shoulder in 2015, and numerous nagging problems in his forearm and shoulder throughout his career.

The Dodgers took a chance by signing him in the winter, after he completed a brief season of relief with the Padres.

"What I knew about him," Dodgers manager Dave Roberts said, "is he's an intelligent guy, cerebral, big arm, really good stuff."

Morrow said he spent last offseason building muscle. He had lost 25 pounds recovering from shoulder surgery and enduring a bout of valley fever.

Then with the Dodgers, Morrow simplified his repertoire to three pitches. Each increased in velocity by two to three miles per hour.

"He resolved himself to pitching out of the pen," Roberts said. "That was a major hurdle for him mentally. So once he kind of conceded that it allowed him to thrive in this situation.