DUNEDIN, Fla. -- Orioles closer Zach Britton is making progress in his rehabilitation from December surgery to repair a torn right Achilles tendon.
Britton was originally forecast to miss six months, but hopes to return in late May. He's on the 60-day disabled list.
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The left-hander has begun running on an underwater treadmill, and he's throwing wearing a protective boot. Britton expects to ramp up his rehab at the end of next week because that will mark 12 weeks since his surgery.
Britton will be able to throw without the boot on Thursday, but doesn't want to get ahead of himself.
"You can't really do too much more than what I'm doing," Britton said. "I would think when I start throwing [without] the boot, and I feel good out of that, and long toss, then it starts meaning more, maybe get on the mound a little sooner. … Come May, we can start pushing the envelope a little bit if everything is going well."

• The Orioles have scratched right-hander Gabriel Ynoa from his scheduled start Saturday against the Pirates due to a stress reaction from shin splints. Ynoa had an MRI on Friday. He'll be out two to four weeks, manager Buck Showalter said.
Ynoa will be replaced by left-hander Jayson Aquino.
• Chris Davis, who has been out since Saturday with a sore right elbow, hopes to return to baseball action early next week, Showalter said.
• Chris Tillman, who threw 61 pitches in a simulated game on Thursday, is still not scheduled to throw in a regularly scheduled Grapefruit League game.
• The Orioles reassigned two right-handed pitchers to Minor League camp, Tim Melville and Asher Wojciechowski.
Melville, who has gone 0-2 with an 11.05 ERA in six games with the Reds, Twins and Padres over the last two seasons, had a 3.38 ERA in three Grapefruit League games.
Wojciechowski, who went 4-4 with a 6.64 ERA in 30 games with the Astros and Reds in 2015 and '17, was 1-0 with a 5.40 ERA in three games this spring.
The Orioles now have 49 players in camp.

Up next
Due to the injury to Ynoa, Aquino will start against the Pirates on Saturday at 1:05 p.m. ET at Ed Smith Stadium in Sarasota. Aquino, who pitched briefly for the Orioles over the last two seasons, was given a non-roster invitation to Spring Training. He hasn't allowed an earned run over three innings this spring.