LOS ANGELES -- Zack Greinke, dealing with arm soreness in recent days, will start Game 4 of the American League Division Series for the Houston Astros on Thursday, opposing Oakland Athletics right-hander Frankie Montas.

Astros manager Dusty Baker said he is "not really sure" what Greinke can provide.

Greinke, 36, hasn't completed six innings since Sept. 8 and has a 5.79 ERA over his past four starts. His most recent outing came nine days ago, in Game 1 of the wild-card series, when he gave up one run but recorded only 12 outs against the Minnesota Twins.

Baker revealed that Greinke was dealing with general arm soreness after Tuesday's game. But the right-hander was able to throw off flat ground at low intensity in Dodger Stadium later that afternoon, shortly after doctors determined that his arm was structurally sound. The news helped Greinke "ease his mind," Baker said, prompting him to move forward with the start.

Cristian Javier, who started 10 games during the regular season and has made two relief appearances during the postseason, is "probably" available out of the bullpen in Game 4, Baker said.

The Astros, one win away from advancing to their fourth consecutive AL Championship Series, don't have any set pitching plans in the event that the A's force a decisive Game 5. Their options will be further limited if Greinke can't provide much length.

"I'm hoping to get as many quality innings as he can give us," Baker said.