GLENDALE, Ariz. -- Dodgers ace Clayton Kershaw took another step toward normalcy on Thursday when he threw a 30-fastball bullpen session at Camelback Ranch.

Manager Dave Roberts said Kershaw was “pretty positive” about the outing and “the life to the fastball was good.”

Roberts said Kershaw decided not to throw breaking balls and would take two days off, then throw another bullpen session with “his arsenal.”

The slow progression to build his pitch count means Kershaw either won’t be ready for Opening Day or would be limited in innings. Kershaw's work Thursday followed a 20-pitch bullpen session on Monday. Usually, bullpen sessions are followed by live batting practice before advancing to game action.

Roberts, who named Kershaw to a ninth consecutive Opening Day start before the left-hander's shoulder acted up, has left the door open for Kershaw to be ready for the start of the season, even though he’ll be five Spring Training starts behind the rest of the rotation.

Kershaw, who signed a three-year, $93 million contract in November, spent the winter recalibrating his body to better sync with his mechanics after experiencing a drop in fastball velocity.

His first two bullpen sessions in Arizona went without a hitch, but after a live batting-practice session and a bullpen session two days later, Kershaw complained of shoulder discomfort.

He received anti-inflammatory medication and treatment and was shut down for several days, followed by 10 days of throwing that led to the pair of bullpen sessions this week.