David Buchanan relied heavily on his cutter, sinker and change-up last season through the first 20 major league starts of his career.

He had changed his grip on his curveball in spring training, when his cutter and slider began to blend together, and he utilized the pitch much less than his others. Refining his curveball has been a point of emphasis this offseason for the 25-year-old righthander as he readies for spring training, where he will compete for a spot in the back end of the Phillies' starting rotation.

The last few weeks, Buchanan has been throwing bullpen sessions in Clearwater, save for the time he spent in the Philadelphia area last week to attend several of the annual winter banquets hosted by the Phillies' minor league affiliates.

"I had success with (my curveball) in certain games," he said. "It started coming along there toward the end. But it's definitely something that has a lot of work still to go. It's definitely something I'm working on. It's getting better, which is all I can ask for."

Buchanan threw his curveball only 9.4 percent of the time, according to Pitch F/X data. He used it mostly with two strikes. An area he needs in which he needs to improve is finishing off batters out when he's ahead in counts. When down 0-2, hitters facing Buchanan last year hit a mystifying .321.

Consistency and throwing strike one are also focuses for the quick-working Buchanan, who recorded a 3.75 ERA but also averaged just less than six innings an outing in his first year in the majors. Working ahead more and forcing contact earlier in counts will help him pitch deeper into games and in turn help the Phillies better preserve their young bullpen arms.

Behind Cole Hamels, Cliff Lee and Aaron Harang, there is an open competition for the Nos. 4 and 5 spots in the Phillies' rotation. Buchanan, Jerome Williams and Miguel Alfredo Gonzalez are the leading candidates, though the Phils could for depth purposes add another arm to the mix before spring training starts on Feb. 19.

Righthander Jonathan Pettibone and lefthander Adam Morgan, both coming off shoulder surgeries, could factor in to the equation if either proves his health in the spring.

“There’s going to be some competition,” Phillies general manager Ruben Amaro Jr. said last week. “I think that’s the only way that you can get better is by creating competition. I can’t sit here and tell you today that David Buchanan’s going to be one of our guys in the rotation, but he absolutely is going to get an opportunity to pitch in spring training and be ready and compete for one of those spots.”