Taijuan Walker will get a belated birthday present on Friday at Minute Maid Park. The Mariners' top pitching prospect, who turned 21 two weeks ago, will make his Major League debut against the Astros.
"Usually on the night before my starts, I don't sleep. I go to bed around 3 [a.m.] for some reason," Walker said. "I just sit up all night doing nothing. I feel like on my start day, I feel like a new person. Everything just goes away. I will be ready."
The right-hander was the Mariners' first selection in the 2010 Draft as a supplemental first round selection (43rd overall) out of Yucaipa High School in California. He's played in the past two All-Star Futures Games and is ranked as the No. 4 overall prospect in baseball by MLB.com.
"I just want him to go out there and do what he does, just be himself, enjoy the experience and have fun," Mariners manager Eric Wedge said. "Hopefully, he'll be able to allow himself to relax and have fun with it. That's the best way to have early success, just really enjoy the moment."
Starting the season with Double-A Jackson, where he went 4-7 with a 2.46 ERA in 14 starts, Walker was then promoted to Triple-A Tacoma, where he went 5-3 with a 3.61 ERA in 11 games. In 114 1/3 innings, Walker has 160 strikeouts and 57 walks with a 1.196 WHIP.
Many of the Astros' younger players have faced Walker before in the Pacific Coast League and know what he brings to the table.
"He's their top prospect for a reason," Astros manager Bo Porter said. "Obviously, it's electric stuff. He's had great success in the Minor Leagues and our guys are going to be up for the challenge."
Right-hander Brad Peacock, who has been solid in his third stint with the Astros this season, will face Walker. He's 2-1 with a 2.88 ERA in his last four starts, allowing only 17 hits in 25 innings.
In his previous outing against the Blue Jays, Peacock (3-4, 5.67 ERA) allowed four runs on six hits in 5 2/3 innings for the win. Striking out five batters in the contest, it marked Peacock's second straight victory.
Mariners: Morse dealt to O's
Outfielder Michael Morse, who was out of the lineup for Thursday's game against the Astros after being claimed by the Orioles, was traded to the O's on Friday for prospect Xavier Avery.
After hitting .248 with nine home runs and 14 RBIs in the first 25 games of the season, Morse struggled after breaking his right pinkie finger and then injuring his hamstring. In 51 games after May 1, Morse added just four home runs and 13 RBIs while hitting .214.
Avery has batted .259 with 29 stolen bases in 120 games between Double-A and Triple-A this season in the Orioles' system. He will be assigned to Triple-A Tacoma by the Mariners.
Astros: Corporan and Stassi making progress
Catchers Carlos Corporan and Max Stassi are making strides after their concussions.
Corporan took a foul ball off the mask on Aug. 19 and Stassi was hit in the head by a pitch on Aug. 21.
"Everything is looking good," Corporan said. "I'm feeling better every day and have no more headaches. I'm happy to be back to normal. That wasn't fun."
"I'm a lot better," Stassi said. "I got a lot of sleep when I was left behind here [while the team went to Chicago] and the only thing is my balance isn't there and there's a little dizziness still. If it doesn't get better in a couple of days, I'll see a balance specialist."
• The Mariners have hit 50 home runs in the seventh inning or later this season, which ranks second in the American League.
• When the Astros hit no home runs in a game, they are just 8-44 this season.
Quinn Roberts is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.