The Phillies' starting rotation threw more curveballs last season than all but three other staffs in baseball. The pitchers offered curveballs for 15.8 percent of their pitches, a mark that had not been neared by a Phillies rotation in more than 10 seasons.

That number was not aided much by Vince Velasquez, who has what is likely the most electric arm in camp. The righthander relied on his blazing fastball — which zipped last season at an average of 93.7 mph — to rack up the franchise's highest strikeouts-per-nine innings ratio since 1997. He threw curveballs for less than 10 percent of his pitches.

The righthander's fastball flashed dominance. And now Velasquez is working to master his curveball.

"It was a good pitch to use, but I didn't really use it as much as I should have," Velasquez said. "I really didn't command it as much. I'm trying to lock in on one target and try to hit that every time. I utilized it a lot in the offseason in bullpens. I'm trying to master it as much as I can. I know it's a good out pitch to use, but I also have a high percentage of getting guys out with my regular fastball. If I can move up and down in the zone, getting ahead of guys and putting guys away with it, then I'm definitely going to use it."

Velasquez's season — his first as a full-time starter — ended in early September because of an innings limit. Velasquez said he does not expect to be limited this season. He struck out 152 batters in 131 innings.

Velasquez was both brilliant (a May shutout with 16 strikeouts) and human (allowing nine runs in an August loss) in a season that showed he could blossom into a top-of-the-rotation starter. If that is the case, the development of the curveball could be crucial. His fastball — the 13th fastest last season among all MLB starters — could be even more dangerous with a developed secondary offering.

"It's a process," Velasquez said. "I'm still learning. It's going to take time. It's going to take all of spring."