Lucas Giolito (Alex Brandon/AP) Lucas Giolito (Alex Brandon/AP)

Lucas Giolito, the Nationals’ 2012 first-round pick who underwent Tommy John surgery in August, is back on the mound and has thrown three bullpen sessions. His first bullpen was 25 pitches last week and he threw 30 in his last two.

Giolito, 18, is rehabbing from elbow ligament replacement surgery he underwent last August. He first picked up a baseball after surgery on Feb. 6 and, in two-week increments, increased the distance from which he was playing catch.

“Really good,” he said of his recent bullpen sessions. “My arm feels great.”

Giolito, a 6-foot-6 right-handed starter who hit 100 miles per hour in high school, strained his ulnar collateral ligament in his right elbow during the spring of his senior season at Harvard-Westlake School in Los Angeles. Both the Nationals and Giolito agreed to continue rehabbing the injury after he signed for $2.925 million following his 16th overall selection in last year’s draft.

In his first professional baseball game on Aug. 14, Giolito was pulled because he experienced soreness in his elbow after throwing two innings in a Gulf Coast League outing and later underwent surgery.

This spring, he said his arm felt strong and he no longer had the mental reservation of a potential re-injury. Barring any setbacks, he expects to appear in the GCL later in the season, although the details are unclear now. Giolito’s estimated major league arrival is 2016.