PHOENIX -- Drew Pomeranz had been traded before -- twice, in fact. He knew the signs.
When the big left-hander returned from a December trip to Texas for a checkup on his surgically repaired shoulder, the missed calls from his agent and from members of the A's front office were a dead giveaway.
Pomeranz was headed to San Diego -- in exchange for Yonder Alonso and Marc Rzepczynski. For Pomeranz, it was a chance to revitalize his career, one which had stalled in Colorado before some brief and inconsistent success in Oakland. For the Padres, it meant taking a chance on a starter with a high ceiling -- or, at the very least, a live bullpen arm.
Suffice it to say, the move has worked out for Pomeranz, and it's worked out for San Diego. Only Randy Jones in 1975 (1.58) and Jake Peavy in 2007 (1.64) -- arguably the two best pitchers in franchise history -- have begun a season for the Padres with a lower ERA than Pomeranz's 1.70 mark through nine starts.
"I just forget about Colorado; it was a really weird time there," Pomeranz said. "The opportunity I had in Oakland let me reset everything. ... I had a chance to figure some things out. Then I come here, obviously there was going to be opportunity. They gave me a shot to start, I stumbled upon a cutter and everything has just fallen the way it should."
The No. 5 overall selection by Cleveland in the 2010 MLB Draft, Pomeranz was shipped to Colorado as one of the main pieces in the Ubaldo Jimenez trade. He struggled there, as the Rockies experimented with a quirky four-man rotation and odd pitch limits. Pomeranz was moved to the bullpen and dealt to Oakland, where he showed flashes of inconsistent brilliance. But the talent was clearly there, and in the Padres' eyes, they were buying low.
That's not to say either side expected this kind of immediate renaissance. At times this season, the 27-year-old southpaw has been downright unhittable. This month, opponents are batting .126/.224/.175 against Pomeranz, and he's allowed just 13 hits in 31 innings.
"I don't know if you can ever expect a sub-2.00 ERA," Padres pitching coach Darren Balsley said of his reaction to the trade. "But I was excited -- big lefty, high pick in the past, a lot of talent there. I've always thought, just looking at him from the other side, this guy can and should be a pretty dominant Major League pitcher."
The biggest change in Pomeranz's game upon arriving in San Diego was the club's insistence that he throw more curveballs. It wasn't just a small uptick. He has thrown the pitch 41.4 percent of the time this season. Only Rich Hill of the A's has thrown a breaking pitch more frequently.
It's also in stark contrast to the rest of Pomeranz's career.
"It's one of the best left-handed curveballs I've seen in a while," Balsley said. "I don't like to compare and say, 'His is as good as [Clayton] Kershaw's.' But his falls into that category as a top-notch curveball. It's impossible -- but it appears it picks up speed and spin, the closer it gets to the hitter."
After they squared off on May 1, Kershaw himself called Pomeranz's curveball "one of the best I've seen in a long time" -- high praise considering the source.
Manager Andy Green believes it's the late break that allows Pomeranz enough deception to throw his curve so frequently. Balsley believes it's the precision. They're both right.
But in Pomeranz's eyes, he's throwing three separate pitches -- all curveballs -- to comprise that 41 percent. He's always thrown a slow looping curve which ends up in the zone. Pomeranz calls that his "get-me-over" hook. This season, he's established the back-door breaking ball to right-handers, which appears to be outside but sneaks back across the plate. And Pomeranz has now perfected the curve that bites hard down and in on righties and away from lefties.
Pomeranz has honed all three of those under the watchful eye of Balsley, who has given the lefty the freedom to throw them in any count.
"Balsley watches you, he sees how you attack guys, he sees who you are as a pitcher and he helps you along that path," Pomeranz said. "He's not trying to direct you toward his path. Some teams want to put their stamp on you when you're young. They want everyone to throw and be a cookie-cutter.
"Bals is very knowledgeable about pitching, and he'll give you tidbits here and there -- this could help you a lot, that could help you a lot. 'Try this, try that.' He just kind of helps you along your path. That's what works. We're all here for a reason. We all made it here because we're talented on our own."
It's not as though Pomeranz's success is solely attributable to his curveball. According to Statcast™, his four-seam fastball has the eighth-highest spin rate among pitchers who have thrown it at least 100 times this season. Opponents are batting just .186 against the heat, and Pomeranz has used it for 25 of his 60 strikeouts.
Then there's the cutter -- a pitch that came about during a simple game of catch with former Minor League teammate Travis Higgs during the offseason. Pomeranz noticed some late movement on Higgs' throws and asked, "What was that?"
Higgs showed Pomeranz how to grip the pitch and where to apply pressure. Shortly thereafter, it became a long-sought-after third pitch in Pomeranz's arsenal.
"I had all the pieces there," Pomeranz said. "It was about organizing them, coming into spring. I was feeling pretty good, so I asked Andy to give me a shot at starting."
The first-year skipper obliged. Pomeranz didn't make his first start until mid-March, but it soon became clear he'd be worth the most to San Diego in the starting five. He wrapped up a rotation spot on the final day of camp -- and since then, he has developed into a bona fide All-Star candidate.
"When we saw his curveball in Spring Training and encouraged him to throw it more often, I think it was pretty obvious right away he was a really good option for us [in the rotation]," Green said. "From there, he's exceeded all expectations."
AJ Cassavell covers the Padres for MLB.com. Follow him on Twitter @ajcassavell. This story was not subject to the approval of Major League Baseball or its clubs.