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3/22/2014 1:29 P.M. ET

Machado could test knee, calf Sunday

PORT CHARLOTTE, Fla. -- Orioles manager Buck Showalter suggested prior to Saturday's game against the Rays that third baseman Manny Machado could run to test his left knee and calf as soon as Sunday.

Machado's rehab had been shut down recently due to issues with scar tissue breaking up in his knee and a mild strain in his calf.

"He was telling me the two days off really did the calf well," Showalter said. "I would bet he'd probably test that [Sunday]."

Machado said he still would not rule himself out for the season opener and, though Showalter agreed, the O's skipper said Sunday's test could be the determining factor for Machado's Opening Day status. If the third baseman doesn't come through the test pain-free, it will be very unlikely he'll be ready to take the field on March 31.

Showalter also confirmed Saturday that once Machado is ready, he will play only in Minor League games for the rest of spring. That way, if necessary, the Orioles can backdate his disabled-list stint to Saturday, making him eligible to come off the DL as early as April 6.

Buck still considering options at top of order

PORT CHARLOTTE, Fla. -- With Opening Day nine days away -- and Manny Machado's status still in doubt -- manager Buck Showalter said he's considering a few different options for what the top of his batting order might look like come March 31.

The belief for now is that Nick Markakis will hit leadoff, but from there it's unclear. Assuming Machado is not ready to suit up for the season opener, Showalter said he's still deciding, though he did not list specific names.

"I'm considering some guys," Showalter said. "It's pretty easy if you don't mind stacking up left-handers, but it'll be related to the other team's bullpen and starters. Those kinds of things."

Johan progressing, throwing off half-mound

PORT CHARLOTTE, Fla. -- Veteran left-hander Johan Santana threw off a half-mound for the first time on Saturday as he continues to work toward a comeback.

Orioles manager Buck Showalter said all went well with Santana's first session, and the southpaw will throw off a half-mound again on Monday, and possibly once more thereafter, before moving to a full mound.

"He drew quite a crowd," Showalter said. "He's on a five-man [rotation] program. He's doing well."

Santana missed the entire 2013 season after undergoing his second shoulder surgery in three years. A two-time Cy Young Award winner, Santana last pitched in the Majors in 2012, going 6-9 with a 4.85 ERA over 21 starts with the Mets, while also throwing a no-hitter.

Paul Casella is a reporter for MLB.com. Follow him on Twitter @paul_casella. This story was not subject to the approval of Major League Baseball or its clubs.