Mariners call up top prospect Walker

Taijuan Walker will make his Major League debut Friday in Houston after the Mariners announced Wednesday night that they'd be calling up their No. 1 prospect from Triple-A Tacoma.

The 21-year-old will become the fifth-youngest player in Mariners history to make his Major League debut as a starting pitcher when he faces the Astros that day. The right-hander, who will officially be promoted Friday before the game, will oppose Houston righty Brad Peacock.

Walker has turned in stellar numbers in his fourth Minor League season, especially in his last two starts. The Mariners' first-round pick in the 2010 Draft, promoted to Triple-A on June 21, went 9-10 with a 2.93 ERA and 160 strikeouts in 141 1/3 innings between Double-A Jackson and Tacoma. His 160 strikeouts rank him fourth in the Minors.

"All my hard [work] has finally paid off, but it doesn't stop here," he wrote on Instagram. "Just want to say thank you to all my family, friends and fans who supported me the whole way and were behind [me] through the good and bad."

Walker, who will wear No. 27 in Seattle, will be just 21 years and 17 days old in his debut -- Felix Hernandez was the youngest player to start a game for Seattle when he allowed one earned run in five innings as a 19-year-old in 2005.

The former Southern League All-Star features a fastball, a curveball and a changeup, with the heater being his best pitch. The youngest pitcher in the Southern League last season, Walker was named the Pacific Coast League's Pitcher of the Week on Aug. 26 after turning in a pair of dominant outings -- he held Tucson to one run over six innings with nine strikeouts in his last start Aug. 25 after blanking Colorado Springs over five frames for the win Aug. 20.

He posted a 4-7 record with a 2.46 ERA in 14 starts at Jackson before going 5-3 with a 3.61 ERA in 11 games for Tacoma. In 25 starts, he's allowed 11 homers, walked 57 and held opponents to a .217 average.

The Mariners announced the move Wednesday night on Twitter.

"Welcome to the bigs, @tai_walker. He'll be on the mound this Friday vs. the #Astros," the team wrote.

Walker was the Mariners' Minor League Pitcher of the Year in 2011 and was selected to the 2012 and '13 All-Star Futures Games. He's currently ranked as the No. 4 overall prospect by MLB.com.

In four seasons, the 6-foot-4 righty is 23-26 with a 3.49 ERA in 371 2/3 innings over 72 games.

Selected 43rd overall in the 2010 Draft out of Yucaipa (Calif.) High School, Walker spent all of last season with the Double-A Generals and went 7-10 with a 4.69 ERA and 118 strikeouts over 126 2/3 innings. In 2011, his first full season in the Minors, he was 6-5 with a 2.89 ERA in 18 starts for Class A Clinton, prompting the Midwest League to name him the circuit's top prospect.