ATLANTA -- Imagine if the Phillies could add a 12-year veteran reliever with 137 career saves, 11.9 strikeouts per nine innings, and a 2.90 earned-run average to their bullpen by the trade deadline.

David Robertson can almost envision it.

Robertson threw a 19-pitch bullpen session here at SunTrust Park on Wednesday before the Phillies continued their three-game series against the Atlanta Braves. It represented the latest step in his protracted return from a right forearm strain, and he emerged more encouraged than after his previous bullpen session, last Sunday in Miami.

"It was the first time that I think I really let the ball go," Robertson said. "I felt really good. I was able to throw the ball with conviction. Kind of got tired there towards the end, so I had to cut it short just a few pitches. But I felt good about it. It's the first time that I really let it rip."

Next up: Robertson is planning to play catch Thursday, then incorporate his curveball in a flat-ground throwing session Friday in New York and test his arm again with a rigorous bullpen session Sunday.

And if all goes well, Robertson said, he would like to face hitters in a live batting-practice setting when the Phillies return from the All-Star break before going out on a minor-league assignment.

It would be a long time coming for Robertson, who hasn’t pitched since a two-inning appearance April 14 against the Miami Marlins. At the time, he hoped he would miss only a few weeks. But the pain in his elbow and forearm took longer than he expected to dissipate.

Robertson, who made at least 60 appearances in nine consecutive seasons before this injury curtailed him, mixed in a few change-ups among the fastballs Wednesday. The curveball is the last pitch to come along.

"I've spun some already, but I want to spin some with a little more conviction," Robertson said. "It's looking good. I'm very happy. I was glad I was able to throw the ball the way I did this time."

Extra bases

Including his gem Tuesday night, Aaron Nola is the seventh Phillies pitcher to throw at least seven innings, allow no more than one earned run, and rack up at least eight strikeouts in three consecutive starts. The others: Steve Carlton, Grover Cleveland Alexander, Roy Halladay, Cole Hamels, Cliff Lee, Curt Schilling, and Randy Wolf. ... Zach Eflin (7-7, 3.34 ERA) will start Thursday night against Braves All-Star right-hander Mike Soroka (9-1, 2.13).