Late bloomer or flash in pan? Red Sox lefty Drew Pomeranz has plenty to prove in move to AL

Pomeranz set to make Red Sox debut (1:27)

The Baseball Tonight previews Wednesday's matchup between the Giants and the Red Sox, with Drew Pomeranz making his Boston debut after being dealt from San Diego. (1:27)

BOSTON -- As much as almost any hitter in baseball, San Francisco Giants outfielder Angel Pagan has faced Drew Pomeranz at every stage of the lefty's winding career -- in 2012, when he was a fledgling starter for the Colorado Rockies; in 2015, when he was sent to the bullpen by the Oakland Athletics; this season, when he emerged as an All-Star with the San Diego Padres.

But as Pomeranz makes his Boston Red Sox debut Wednesday night at Fenway Park, not even Pagan knows what to expect.

"It's tough to say because he's changing leagues. It's totally different," Pagan said. "Is he a great pitcher that's having a great year? Yes. We just have to wait and see how that transition from National League to American League goes. I can not predict."

And that's what makes the Red Sox's trade for Pomeranz last week so uncertain.

Last season, three proven aces were dealt before the trade deadline. Although there wasn't any guarantee that Cole Hamels, Johnny Cueto or David Price would pitch well for their new teams, their track records suggested a level of reliability, if not excellence.

That doesn't exist with Pomeranz. Before he broke out with a 2.47 ERA and 10.1 strikeouts per nine innings through 17 starts with the Padres, numbers that earned him a spot on the NL All-Star team, he had a 4.07 ERA and 8.1 strikeouts per nine innings in 107 career appearances, only 49 of which were starts. In those starts, he posted a 4.60 ERA and 7.7 strikeouts per nine.

But Pomeranz also was arguably the best starter available at a time when the demand for starting pitching far exceeds the supply. Several AL contenders, including the rival Baltimore Orioles, are looking for rotation help, so Boston struck early by acquiring Pomeranz last Thursday night for prized 18-year-old right-hander Anderson Espinoza. It was a steep price but one that Red Sox president of baseball operations Dave Dombrowski said is being asked by teams that are peddling rent-a-pitchers with expiring contracts.

To hear Red Sox pitching analytics guru Brian Bannister tell it, Pomeranz might be a classic late bloomer. For one thing, the 27-year-old's success this season coincided with the addition of a cutter that diversified a repertoire that consisted of only a fastball and a knuckle-curve. For another, he's under club control through 2018 and would certainly benefit from some continuity after being traded three times in the past four years and four times since 2011.

Bannister also notes that Pomeranz opted to add the cutter rather than hone his changeup, which he uses only sparingly. The fastball-curveball-cutter mix gives Pomeranz the same repertoire as Los Angeles Dodgers ace Clayton Kershaw, who has used it to become only the best pitcher on the planet.

"I feel like a lot of guys are starting to do that. A lot of guys have cutters now," Giants shortstop Brandon Crawford said. "But [Pomeranz's] curveball is a little bit better probably than most. I feel like that's what makes him tough. It's big and sharp. You see the ball coming at you at first and you might kind of flinch and let one go by and maybe chase later in the count."

Indeed, though the cutter "gives him a different look," according to Giants catcher Buster Posey, Pagan believes the curveball remains Pomeranz's "A-pitch." As a result, many of the Giants said they haven't noticed a particularly different pitcher this season. The biggest change, it seems, is Pomeranz's ability to throw his curveball for strikes more consistently.

"It's a big curveball and he throws it for a strike in any count," said Pagan, 2-for-10 in his career against Pomeranz with both hits coming earlier this season. "When a pitcher has the confidence to throw a certain [offspeed] pitch 3-2, when a lot of pitchers throw a fastball, that creates a situation good for him. You see the percentage of chases on that pitch, it would probably be over 50 percent. Even if you look for it, and I have, it's still tough to hit it and square it up for a base hit. That's how good that pitch is."

It isn't only Pomeranz's curveball. Overall, batters are swinging at 30.9 percent of his pitches outside the strike zone, an improvement over his career average of 29.5 percent, according to the data at Fangraphs.com. That likely accounts for the increase in his strikeout total.

"I think he's just pitching with a lot of confidence now," Posey said. "He's had success, obviously, this year. He just seems to be commanding his pitches really well right now."

"A guy that throws like that is a good fit in any ballpark." Giants manager Bruce Bochy, on new Red Sox left-hander Drew Pomeranz

So, perhaps Pomeranz is finally maturing into the pitcher the Cleveland Indians believed he would be when they took him with the fifth overall pick in the 2010 draft, two picks before the New York Mets chose Matt Harvey, eight before the Chicago White Sox grabbed Chris Sale and 33 before the Toronto Blue Jays drafted Noah Syndergaard.

Based on what they gave up to get him, the Red Sox certainly have high expectations for Pomeranz. And the fact that he was issued No. 31 will bring to mind comparisons to another big lefty from the team's recent past: Jon Lester.

"Some guys, they just find a way to grow as a pitcher and he's done that. Give him credit," Giants manager Bruce Bochy said of Pomeranz. "He's always had great stuff, even back to when he was in Colorado. He just put it together this year. Good for him. He's tough. Here, you think you're getting a break when San Diego trades him, and we still see him."

Pomeranz joked that he "can't really get away" from the Giants. He has made seven starts against them, more than any other team, including three already this season. If he hadn't gotten traded, he was scheduled to face them last weekend in San Diego.

It will be a good test, then, to see if he can have success against the team that's more familiar with him than any other. But though the Giants have averaged 4.6 runs per game this season, their offense lacks the potency and especially the depth of AL East powers Baltimore and Toronto.

And lest anyone forget, Petco Park in San Diego is a pitcher's heaven, with AT&T Park in San Francisco and even Dodger Stadium in Los Angeles not far behind. Fenway Park, Camden Yards in Baltimore and Rogers Centre in Toronto tend to be far less forgiving.

Though Pagan prefers to reserve judgment on whether Pomeranz's success in San Diego will translate to Boston, Bochy doesn't.

"A guy that throws like that," Bochy said, "is a good fit in any ballpark."

Only time will tell.