Manager Scott Servais made the announcement Tuesday.
Hernandez has missed three months with right shoulder stiffness. He pitched three-plus innings Monday night for Triple-A Tacoma in his fourth rehab appearance, giving up one run on four hits and three walks while striking out five.
"Command of the fastball, as expected, wasn't as pinpoint as he would have liked it, but he felt healthy," Servais said. "So he will slide into our rotation on Saturday."
Hernandez last pitched for the Mariners on May 11. In eight starts this season, the 33-year-old righty is 1-4 with a 6.52 ERA.
Hernandez won the American League Cy Young Award in 2010 and has finished among the top four in Cy Young voting three other times. He has had injury setbacks in each of the last four seasons, winning a combined 26 games in 77 starts.