TUCSON, Ariz. -- As if the Dodgers don't have enough uncertainty with their fifth starter, they're not too sure about their third starter either.

Thirteen days before Chad Billingsley is scheduled to face the Padres in Game 3 of the regular season, he's off-schedule because of a strained right groin.

He did not test the injury throwing off a mound Thursday, as originally planned. Instead, Billingsley made 15 pitches out of a windup on flat ground, with left-handed pitcher Hong-Chih Kuo doing the catching.

Billingsley said he hoped to have a bullpen session Friday. Manager Joe Torre, before the Dodgers' Thursday game with the Rockies, confirmed that, but also said Billingsley has been scratched from his scheduled Sunday Cactus League start against San Diego, and instead would throw a simulated game Sunday on the Minor League side, if he's healthy enough.

Meanwhile, Torre said that Claudio Vargas' elbow was sore after he was hit hard in a one-inning appearance Wednesday, perhaps because of a new grip on a slider. Vargas, signed to compete for the fifth-starter job, has allowed six home runs in 15 1/3 innings with an 8.22 ERA.

Another change in the schedule: Relievers Jonathan Broxton and Cory Wade, instead of having bullpen sessions Thursday, threw in a simulated game back at Camelback Ranch-Glendale. Broxton, working after a week off, was touched for four runs and a blown save Tuesday night in his first game back from the World Baseball Classic.