WEST PALM BEACH, Fla. -- The Astros trimmed their Spring Training roster to 33 players on Sunday. Five players were sent to Minor League camp.
Outfielder Kyle Tucker, the Astros' No. 2 prospect, according to MLB Pipeline, along with infielder Jack Mayfield, outfielder Jon Kemmer and catcher Garrett Stubbs were reassigned to Minors camp, and right-handed pitcher Francis Martes was optioned to Minors camp.
"We did want to thin the room out a little bit and get down to, really, all the guys that are in the competition," manager A.J. Hinch said before Sunday's game with the Braves. "The conversation is getting a little tougher, because there are guys that have an argument that they should get more of an opportunity or be in the conversation, specifically a guy like Martes today. But we've got some tougher conversations to have that will happen over the next week."
:: Spring Training coverage presented by Camping World ::
Martes appeared in four games this spring. He started two games, and that's where Hinch said he believes the right-hander's future is in the big leagues.
"There's an argument that he could be in our bullpen right now. We want him to start, which is the main reason why we wanted to send him out," Hinch said. "He's going to start next week in Fort Myers [against Boston]. He's going to start [Monday] in Triple-A, and then we're going to give him a few more innings."
The 22-year-old posted a 1.93 ERA this spring, striking out 13 in 9 1/3 innings. He pitched in 32 games last season for the Astros, starting four.
"The development has come fast. He got up to the big leagues very quickly," Hinch noted. "He got pushed to the bullpen based on need. We want to make sure he continues to develop as a starter.
"The third pitch this spring [his changeup] has been very good. He's refined his delivery to the point where it's under control and he can repeat it a little more effectively. His stuff is high-end. We have to remind ourselves that he's still in his early 20s, and he's still in development stage, and that's going to happen in Triple-A."

Tucker had an outstanding spring, slashing .410/.429/1.223 in 39 at-bats. He hit four homers and drove in 17 runs, and Hinch said he liked the way Tucker blended in with the veterans in camp.
"He's a good player and has a bright future," Hinch said. "We gave him a couple of things that he needs to work on. He's going to be in Houston for the exhibition series. So you'll see him again in our camp.
More seasoning against left-handed pitching is what Hinch is hoping to see from the left-handed-hitting right fielder.
"That'll be key for him. I think, defensively, you're going to see him play a little more in left field and right field and not primarily stay in right field like he's done," Hinch said.
"The pace of play here is a little bit faster, and I think that's something that opened his eyes, whether it's small details like getting the ball to the cutoff man a little faster when the ball comes off the wall, to how we shift and how we play in the outfield. I think it's just a general step forward in a couple areas before he's ready."
Hinch added that Tucker has a "good chance" to potentially be in an Astros uniform this season if the need arises, and that he's the right guy to call up.