MLB Game Preview - Washington at Oakland

Sun Jun 4, 2017 4:05 PM EDT

OAKLAND, Calif. -- The Washington Nationals can't complain about how they've done while sluggger Bryce Harper served his three-game suspension for fighting San Francisco Giants reliever Hunter Strickland on Monday after being drilled by a pitch.

But after winning two of three games without Harper, they'll still be happy to have him back for the finale of their three-game series against the Oakland Athletics on Sunday afternoon at the Oakland Coliseum.

"He's a game-changer," said Nationals right-hander Tanner Roark, who will make his 12th start of the season and face A's righty Sonny Gray. "He's having a tremendous year. He's not going to hurt us being out there. It will be good to have him back."

Harper, who was the National League MVP in 2015, is batting .328 with 12 doubles, 15 home runs, 43 RBIs and 44 runs. He has a slugging percentage of .655 and an on-base percentage of .438.

Harper has been at his home in Las Vegas while serving his suspension.

"I know he's working," Nationals manager Dusty Baker said before a 10-4 loss to Oakland on Saturday that evened the series. "He went home to work, work with his dad, work out. I'm not worried about him just lounging. He'll be back tomorrow and I plan on him being in the lineup tomorrow."

Roark (5-2) has put up some stellar numbers of his own over his past two starts, a 5-1 win against Seattle on May 24 and a 3-0 victory against San Francisco on Monday.

Roark allowed one run on eight hits over seven innings versus the Mariners, striking out eight and walking none. Then against the Giants, he threw seven shutout innings, allowing six hits while fanning six and walking one.

"I felt more myself," Roark said of his past two starts. "I think early on I was thinking too much, which is always not a good idea."

Roark credits a tip from pitching coach Mike Maddux for helping him get back on track after a nightmare start at Pittsburgh on May 18. He gave up seven runs on eight hits over five innings in a 10-4 loss to the Pirates. Maddux thought he might be gripping the ball too tightly.

"I wasn't having the movement on my stuff as I would like, like a ride back to a lefty or whatever," Roark said. "That wasn't there. I was just missing by that much. I just couldn't figure out why."

So Roark loosened his grip, and the movement on his pitches returned. So did the positive results.

After pitching back-to-back gems, Gray (2-2) struggled in his last start on Tuesday at Cleveland. Gray allowed seven runs on nine hits over 4 2/3 innings with three strikeouts and two walks in a 9-4 loss. In his previous start, he allowed one run on three hits over seven innings and struck out 11, one off his career high.

"He started out pretty good but maybe hit a little bump in the road where he didn't feel great about his stuff and maybe his command wasn't as good as a couple previous times before that," A's manager Bob Melvin said of Gray's start against Cleveland.

In his only career appearance against Washington, Gray had a no-decision May 10, 2014, at the Coliseum. Gray allowed three runs on six hits over seven innings in a 4-3, 10-inning A's victory.

Roark had a no-decision in that game, too. He allowed one run on two hits while striking out five and walking none over 7 2/3 innings.