While Mike Mussina took the first steps toward a return to the Orioles' rotation, throwing lightly off a mound Sunday, the Orioles are plotting a cautious course for their starting pitchers over the final four weeks of the season.

Mussina, who hasn't pitched since being hit with a line drive on his right shoulder Aug. 22, said today his bullpen session Sunday "went fine," but that he was still about 10 days away from being able to start. "I need to throw two bullpens full-bore before I'm ready to go," he said.

By Miller's calculations, if Mussina can pitch by the start of the Oakland series on Sept. 14, he can get four starts on his usual four days' rest and a fifth start on the last day of the season (Oct. 3) on three days' rest, if he wants it.

In the meantime, the Orioles plan to skip Sidney Ponson's turn in the rotation next week, and skip Jason Johnson's turn the following week, in an effort to "freshen up" their arms.

"They've both made 28 starts," Manager Ray Miller said. "We want to give them a week to freshen up, and they'll still have four starts left."

Matt Riley, the 20-year-old left-hander who will make his major league debut Thursday in Minnesota, also will be treated carefully.

"I'm not going to pitch him every five days," Miller said. "In my mind, if he pitches five good innings [Thursday], I'll get him out of there, give him five or six days off and let him do it again. I don't want to overextend him, regardless of whether he does well or not."

Another September Call-Up

Dave Machemer, manager of the Orioles' Class AAA affiliate in Rochester, will join the Orioles' coaching staff for the last four weeks of the season. The Red Wings' season ended tonight in Buffalo, and Machemer is expected to join the Orioles in Minnesota on Tuesday. Rochester finished 61-83. . . .

When Jesse Orosco gave up a single to Roberto Alomar in the eighth inning today, allowing Dave Roberts to score, it marked the first inherited runner Orosco had allowed to score since June 23. Orosco had stranded his past 19 inherited runners. . . .

Albert Belle is hitting .349 with seven homers and 25 RBI in his past 32 games.