HOUSTON -- Taijuan Walker's mother, Nellie Garcia, has been his biggest cheerleader throughout his baseball career.
His mother had just one thing to tell her son before his big moment.
"Good luck T.T.," Garcia said, using the nickname he's had since childhood.
Pitching in front of about 40 family members and friends, Walker did not allow an earned run over five innings to help the Mariners beat Houston 7-1. Dustin Ackley had a career-high four hits with four RBIs.
"You only get one debut, so having all of them out here was a great feeling," Walker said.
The 21-year-old right-hander, rated the fifth-best prospect in baseball, yielded two hits and one run with two strikeouts and a walk. If the 6-foot-4 Walker (1-0) had any rookie nerves, it certainly didn't show as he retired the first eight batters he faced.
"He was more and more comfortable as the game wore on and let the ball go a few times," manager Eric Wedge said. "I thought he did a nice job with the secondary stuff, with the breaking ball, with some changeups. He was downhill with the fastball. I thought he was very impressive out there."
The Astros were up by one in the fourth before Ackley tied it with an RBI single. Seattle led by two in the fifth before a single by Ackley made it 5-1. A run-scoring single in the ninth gave Ackley four RBIs to tie a career best. He had the same number of hits as Houston.
Astros starter Brad Peacock (3-5) was tagged for seven hits and five runs in 4 2/3 innings.
Abraham Almonte, also playing his first major league game, added two RBIs to help the Mariners win their second straight following a six-game slide.
Walker relied heavily on a fastball that was routinely clocked at 95 mph, but reached as high as 97 mph. He also used a cutter, curveball and slider to keep the Astros off balance.
"He was really impressive," Houston's L.J. Hoes said. "He's a big kid. On his video, he didn't look as big as he really is. It says he's throwing 96 (mph), but it seems way harder than that because he's so big."
A first-round draft pick in 2010, Walker joined the Mariners after going 4-7 with a 2.46 ERA in 14 starts at Double-A and 5-3 with a 3.61 ERA over 11 starts in Triple-A. He was dominant in his last two outings, going 2-0 with a sparkling 0.82 ERA.
Walker became the youngest starting pitcher to make his debut for the Mariners since Felix Hernandez's first game in 2005 at 19. The Mariners offset Walker's inexperience by starting catcher Henry Blanco, who turned 42 on Thursday. Wedge thought Blanco's presence would help Walker feel more comfortable.
Walker didn't get rattled during a tough third inning for Seattle's defense.
A two-out error by first baseman Justin Smoak gave Houston a 1-0 lead. Hoes singled on a grounder that deflected off Kyle Seager's glove at third base. But after a short visit to the mound by Blanco, Walker retired Jose Altuve to limit the damage.
Walker set down six of his last seven batters, with the only baserunner coming on a walk to Brett Wallace with two outs in the fourth.
Walker was helped by some dazzling defense for the last out of the fifth. Ackley sprinted before sliding on his knees to grab a fly ball hit by Grossman near the bullpen in right-center. Walker pumped his fist and smiled before leaving the mound.
Ackley had a hard time deciding if he enjoyed his defensive work or offensive performance better.
"Man, the catch was pretty fun, I'll have to say that," he said. "I haven't really had many plays like that, so that was pretty sweet. But you can't say that I didn't have fun having four hits. That was pretty fun, too. I don't know. It's all pretty good and pretty exciting."
Walker's cheering section consisted of friends and family who traveled to Houston from California and Louisiana. Several members of the group, which included his mother, father and nine of his 11 siblings, donned his pinstriped No. 44 jersey from the Double-A Jackson Generals. Walker wore No. 27 on Friday night.
Garcia was emotional as she watched her son pitch. She spoke of the hug she shared with her son during the game.
"I think it was one of the best moments of my life," she said. "We've had a lot of moments hugging on the field -- don't make me cry right now. I think that was the realest moment ever."
Walker's father, Frank, smiled broadly as he talked about his son and the opportunity to share this milestone with him.
"It is very exciting," he said. "It's awesome. It's unbelievable. Words really can't describe it."
The Mariners optioned RHP Erasmo Ramirez to Triple-A Tacoma and selected Almonte's contract. Almonte started in right field. ... The series continues Saturday when Seattle LHP Joe Saunders opposes Dallas Keuchel. ... Houston C Carlos Corporan, on the seven-day concussion list, said he no longer has concussion symptoms and is "back to himself." He has been doing individual work, but isn't sure when he'll return. ... Olympic gold medalist and softball star Cat Osterman threw out the ceremonial first pitch.