Oakland hopes recent acquisition Jeff Samardzija is up to the challenge.
As Hernandez looks to continue his push toward earning a starting nod for the All-Star game, Samardzija will try to lead the A's to their eighth win in nine games in his second AL start Friday night in Seattle.
Hernandez (10-2, 2.11 ERA) was originally scheduled to take on Minnesota on Thursday before Mariners manager Lloyd McClendon decided to push him back to face the AL West leaders at Safeco Field.
The move also lines up the right-hander to pitch in Tuesday's All-Star game in Minneapolis on three days rest, then be ready to open the second half against the second-place Los Angeles Angels.
"You want your best pitchers facing your division rivals," McClendon told MLB's official website. "Those are the guys in front of us. I'd be foolish if I didn't want Felix facing Oakland and Anaheim."
McClendon's change makes sense considering Hernandez is 6-1 with a 1.40 ERA during a franchise-record 10 consecutive starts of at least seven innings while allowing two earned runs or less. He's also on pace to set a club record for ERA at the All-Star break, topping Randy Johnson's 2.20 mark in 1997.
The Mariners (49-43), who trail Oakland (58-34) by nine games, could use another extended outing from Hernandez after using six pitchers in an all-bullpen effort in Thursday's 4-2 home loss to the Twins. That came one night after three Seattle relievers combined to throw 5 2-3 innings.
Hernandez is 17-7 with a 2.64 ERA in 32 career starts versus the A's. He beat them twice in April with a 1.76 ERA but had one of his worst games of 2014 in his last start against them, yielding four runs and 11 hits in 6 1-3 innings of a 6-4, 10-inning win May 7.
Seattle has limited the high-scoring A's to 3.1 runs per game and a .214 average while splitting the first 10 meetings.
"It's no different than any other game," said Hernandez, who looks to stop the Mariners' three-game losing streak.
Samardzija (1-0, 1.29), who was named to the NL All-Star team but will not participate, made an outstanding first impression after he was acquired from the Chicago Cubs last weekend. The right-hander allowed one run and four hits over seven innings in Sunday's 4-2 home win over Toronto.
"They were doing just fine without me," he said. "I don't want to come in and change anything and change the atmosphere."
In his only start against the Mariners, Samardzija gave up two runs over seven innings in Chicago's 5-3, 11-inning win at Safeco Field on June 29, 2013.
He's facing a Seattle offense which has been held to nine runs over the club's 2-5 slump, going 4 for 47 (.085) with runners in scoring position.
Robinson Cano and James Jones had three hits apiece Thursday, while All-Star Kyle Seager accounted for the team's only scoring with a two-run homer. Cano, batting .400 over his past 11 games, looks to extend an 18-game hitting streak versus Oakland dating to his time with the New York Yankees.
Stephen Vogt is batting .457 over a 10-game hitting streak after going 2 for 5 with three RBIs in Thursday's 6-1 win in San Francisco, helping the A's take three of four in a home-and-home set.
All-Star Josh Donaldson went 2 for 3 with his 20th home run, but he's batting .163 in 39 career games versus Seattle.
Coco Crisp, hitting .321 against the Mariners in 2014, could be out after sitting Thursday with a sprained ankle.