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De La Rosa, who turns 35 on April 5, said part of his rehab and recovery was spent studying.
"I watched Cliff Lee and Andy Pettitte -- I liked both those guys a lot," said De La Rosa, who went 4 2/3 innings against the Athletics in Tuesday's 6-2 victory and gave up his only runs on a two-run homer by his final batter, Matt Chapman.
Before the injury, De La Rosa relied on a 92-93-mph fastball. Before 2011, the year when he was injured, his fastball useage per season ranged from 54 percent to 62.3 percent. He also used his slider up to 23.5 percent in 2009.
After returning to health, the fastball velocity is down slightly -- 91.4 mph last season. What's up is his use of an 87-88-mph cutter and a split-finger changeup that's in use 27-37 percent of the time, which varies from year to year.
"I learned how to pitch," De La Rosa said. "Before, I just threw the ball. I used to have a really good arm. That year when I was hurt, I watched a lot of video and learned how to pitch."
Of course, he hasn't taken everything from those pitchers. De La Rosa is a quiet guy off the mound, where at times his anger can show.
Of Lee he said, "I wish I could learn to have the composure like him."
De La Rosa's fire isn't the impediment it was during younger years, but he says it's something he still must watch.
"I still [get mad]," De La Rosa said.
But that's during the regular season. He minimized the anger after Chapman's homer Tuesday.
"A little bit, but it's Spring Training," De La Rosa said.