Ryu wouldn't speculate when he would be able to return. Rosters expand on Monday, when it won't be necessary to move a player to make room for Ryu's return. Mattingly said the roster move is part of the decision.
Ryu has allowed only one run in 19 innings this year to the Padres, Sunday's opponent. He hasn't faced the Nationals, Monday's opponent, this year.
Following Ryu to the bullpen mound Tuesday was Paco Rodriguez, still rehabbing from a teres major strain near his shoulder. It was the left-handed reliever's third bullpen session and he's throwing at about 70 percent effort.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.