Rookie southpaw Justus Sheffield did his job again on Sunday, but the Mariners' offense remained quiet in a 3-2 loss, as Houston completed a three-game series sweep with a ninth-inning walk-off homer by Kyle Tucker at Minute Maid Park.

The Mariners have been outscored 29-12 over a five-game losing streak and crossed the plate just four times in the three games in Houston.

• Box score

The Mariners totaled just four hits on Sunday and hit .153 (13-for-85) with 30 strikeouts in the series, which isn’t a good formula against the three-time defending American League West champions. The loss dropped the Mariners to 7-16 on the season, and they are 1-6 against the Astros this year and 2-24 since the start of 2019.

“Losing 2-1 and 3-2 games against this team in this ballpark, you’re disappointed. You don’t win those games,” Mariners manager Scott Servais said. “We did a lot of good things on the pitching side the last couple nights. Unfortunately, they shut us down.”

Sheffield, who picked up his first career win in his previous outing last Sunday against Colorado, delivered another strong start, as he allowed just two runs (one earned) on six hits on 89 pitches over six innings to lower his ERA to 4.12 in four starts.

The 24-year-old has altered his approach this season in abandoning his higher velocity four-seam fastball, and instead working off a two-seamer down in the zone that plays well with his outstanding slider.

“It’s really good,” Servais said. “Throwing strikes is a big thing, and he’s getting his fastball to the glove side, which opens up the slider off of that. I’m really excited with the growth and where he’s headed. The projection is going the right direction, no question about that. He’ll continue to build on those. 

“Once you start putting those type of outings together, your confidence should grow. He has a ton of confidence right now. I love seeing him out there. Unfortunately, we’ve got to get him a few more runs, and that didn’t happen today.”

Sheffield said Sunday’s effort meant even more coming on the 100th anniversary of the founding of the Negro Leagues.

• Dunn, Mariners honor Negro Leagues

“Definitely, 100 percent,” Sheffield said. “It’s one of those things where you kind of step back and recognize that’s the reason you’re even out here playing the game. For us to be able to celebrate the 100th anniversary of the Negro Leagues is huge and amazing. There are not many of us out there, pitchers especially. So to be able to get a start on this day, it meant a lot.”

Two other rookies delivered the Mariners’ lone offensive highlights against Astros starter Lance McCullers Jr., as catcher Joseph Odom picked up his first career hit and RBI, and center fielder Kyle Lewis snapped an 0-for-15 slump with an RBI single in the third to give Seattle a 2-1 lead.

“I don’t worry too much about the hitting part,” said Odom, who was just activated off the taxi squad for this series. “My job here is to help these pitchers go deep into games, give them good targets and use my knowledge with them. But I want to be a well-rounded player and help this team, so it was huge to get that knock, and hopefully that will help me settle in a little bit and get it rolling.”

However, the Astros tied the game back up with a run-scoring single by Martín Maldonado in the fourth and won it with Tucker’s home run off reliever Erik Swanson with one out in the bottom of the ninth. 

Dan Altavilla struck out the side in the seventh, rookie Joey Gerber zipped through a 1-2-3 eighth and Swanson struck out Jose Altuve to open the ninth. But Tucker turned on a 96 mph inside fastball from Swanson, the third homer he’s allowed in 5 1/3 innings over six outings.

“Swanny is throwing the ball very hard,” Servais said. “We’ve seen a spike in his velo, but it’s location. Certainly, in this ballpark, those fly balls tend to not end well. But Swanny is learning. I do like the way he’s aggressive and is attacking, but being able to finish off innings has been a struggle for him. But he’ll get more chances. That’s what this year is about, continuing to give these guys opportunities and let them learn from them. We’ll all be better down the road for it.”