Hernandez met with Mariners trainers and got some medicine on Friday afternoon, but then he was sent back to the team hotel to rest. Servais said he spoke briefly with Hernandez and is hopeful he'll be ready to go in Saturday's middle game of the series.
"We'll see how he is. Fingers crossed, hopefully he's OK," Servais said prior to Friday's game. "If not, we've got to go to Plan B, which we'd probably look at [long reliever] Mike Montgomery or somebody like that. But hopefully he'll be able to go tomorrow."
The rest of the Mariners' rotation has pitched since Monday's off-day, so they'd have to go on short rest if moved up, which is why Montgomery -- a converted starter now working in the bullpen -- would be the likely option.
Hernandez is 1-1 with a 1.00 ERA in three starts on the season, with 20 strikeouts and 13 walks in 18 innings. He's tied with Randy Johnson for the Mariners' franchise record in strikeouts with 2,162 and also is one win shy of tying Jamie Moyer's franchise record of 145.
Hernandez isn't one to miss many games. The 30-year-old has started 30-plus games and thrown 190 or more innings in 10 straight seasons.
"It's pretty odd for Felix. He takes the ball no matter what," Servais said. "I've got to trust the training staff here, and they told me I'd be best to give him a day and make sure he's got his legs under him, because he did not feel good at all."
Getting pushed back in this series means Hernandez will miss the Astros at the start of the next homestand. He was scheduled to throw Wednesday against Houston, but now will presumably pitch in the following series against the Royals at Safeco Field.
Servais wasn't concerned about his ace missing a start against the AL West-rival Astros.
"I'm worried about this series here right now," he said.
Iwakuma is 0-2 on the season with a 4.50 ERA in three starts. The 35-year-old right-hander has had good success against the Angels in his four seasons in the Majors, going 8-3 with a 2.71 ERA in 14 games.
Greg Johns has covered the Mariners since 1997, and for MLB.com since 2011. Follow him on Twitter @GregJohnsMLB and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.