Justus Sheffield seems to get increasingly closer to his first major league victory with every start.

The Seattle Mariners' rookie left-hander is 0-1 through four starts this season, but has allowed just one run in 11 innings over his past two starts entering Sunday afternoon's matchup with the Chicago White Sox at T-Mobile Park.

"The confidence is growing," Mariners manager Scott Servais told reporters of Sheffield. "You can see him making pitches and slowing things down when he needs to. I just think he's under control.

"He put a lot of pressure on himself, certainly, when he was here early (for one game in April), and in Triple-A. He's relaxed (now). He's getting back to doing what he's doing, and trusts his ability at this level. And, it's great he's getting the results right now, too."

On Sept. 2, Sheffield (0-1, 4.43 ERA) pitched five scoreless innings at Wrigley Field in a game the Mariners eventually lost to the Chicago Cubs 5-1. He gave up five hits, walked two and struck out seven.

Last Tuesday at home against Cincinnati, Sheffield allowed one run on seven hits in six innings, with three walks and four strikeouts. He was aided by four double plays.

"I feel good," said Sheffield, who was the centerpiece in the offseason trade that sent lefty James Paxton to the New York Yankees. "I've just got to keep working, keep building off every start. That's what I'm looking forward to doing."

He'll take on a White Sox lineup that features baseball's leading hitter in Tim Anderson (.333) and the American League's leading RBI producer in Jose Abreu (116).

Sheffield has a fastball that averages around 93 mph and an effective slider.

"The movement on his fastball is very unique," Servais said. "It's very late. Sometimes it's darting down, sometimes it's cutting in on the right-handers. It's got late life to it. And then the slider off of those really plays."

And Sheffield is also working to use his changeup more frequently.

"When you're still developing guys at this level, you've got to throw all of your pitches," Servais said. "Certainly his go-to pitches will be his fastball and his slider, and it's probably going to be that for the majority of his career. But, to get through that lineup a third time, you've got to have that third pitch."

The Mariners won 2-1 in 10 innings Saturday as Omar Narvaez hit a solo homer in the 10th inning off Alex Colome, the player he was traded for in the offseason.

The White Sox plan to counter Sheffield with right-hander Ivan Nova (10-12, 4.69) in the series finale. Nova is 0-1 with a 6.87 ERA in four career starts against the Mariners. That loss came April 7 in Chicago, when he allowed seven runs in 2 1/3 innings of a 12-5 decision.

Nova snapped a three-game skid Tuesday in a 7-3 victory against Kansas City, giving up three runs on six hits in 5 2/ 3 innings, with no walks and five strikeouts. The three runs came on solo homers in the opening two innings.

"He did a great job to battle through that," White Sox bench coach Joe McEwing told reporters. "He was missing a lot arm side early, and then getting back on the plate and missing over the plate early. And (acting pitching coach Curt Hasler) came to him, went to talk to him and figured out something mechanically in his delivery, and after that he was able to be his old Nova, getting ground balls and being able to get through it."

--Field Level Media