Phillips (elbow) threw a bullpen session to a squatting catcher March 17, per MLB.com.
Phillips had previously been throwing only to a standing catcher, so this was a notable step forward in his recovery from the Tommy John surgery he underwent last June. The righty reliever is beginning the season on the 60-day injured list and is expected to miss most of the season, though he could be ready for game action sometime in the second half.