Ryan Castellani pitched four-plus hitless innings in his major league debut and three relievers -- Jeff Hoffman, Yency Almonte and Phillip Diehl -- completed a one-hitter as the Colorado Rockies defeated the host Seattle Mariners 5-0 on Saturday night.

Charlie Blackmon went 3 for 4 with two doubles and three RBIs to increase his batting average to .446. He also lifted his MLB-leading hit total to 25.

Castellani, a right-hander who was a second round pick out of high school in 2014 and is considered one of the Rockies' top pitching prospects, retired the side in order in each of the first four innings.

But Castellani, who struck out three, wasn't able to make it through the fifth inning to qualify for the victory.

Seattle's Kyle Seager led off the bottom of the fifth and was hit by a pitch on a 3-0 count. Castellani then walked Daniel Vogelbach on five pitches, prompting a visit from Rockies manager Bud Black and a pitching change to Hoffman (2-0).

Hoffman got Evan White to ground into a double play and Tim Lopes to hit a comebacker, ending the threat.

The Mariners finally got a hit with two outs in the sixth as J.P. Crawford lined a pitch from Hoffman into center field for a single. Hoffman went three innings and Almonte and Diehl pitched an inning apiece.

The Rockies broke a scoreless tie with a four-run fifth.

Ryan McMahon led off with a bloop double down the left-field line off left-handed reliever Anthony Misiewicz (0-1). An out later, Garrett Hampson walked and the Mariners brought in right-hander Joey Gerber.

Trevor Story greeted Gerber with a line-drive single to left to load the bases.

Blackmon then doubled high off the wall in right field to clear the bases. A wild pitch sent Blackmon to third and he scored on Daniel Murphy's single to left.

The Rockies added a run in the sixth on a pair of walks and a two-out, RBI single by Story.

Mariners left-hander Nick Margevicius, making his first start of the season, pitched 3 1/3 scoreless innings, allowing three hits with one walk and three strikeouts.

--Field Level Media