Hernandez will officially sign the pact, which was reported by USA Today Sports last week to be worth a total of $175 million over the next seven seasons, during a press conference scheduled for 5 p.m. (et) on Wednesday.
The two sides had initially come to terms on the record pact last Thursday, but the deal had been held up over concerns by the Mariners over Hernandez's elbow following a physical exam.
Hernandez had two years and $39.5 million on a five-year extension he signed with Seattle prior to the 2010 season. The new arrangement will pay the standout right-hander $25 million annually through 2019.
Hernandez, who turns 27 in April, went 13-9 with a 3.06 ERA over 33 appearances this past season, leading the AL with five shutouts and striking out 223 batters in 232 innings.
The three-time All-Star has started at least 33 games and thrown over 230 innings in each of the last four seasons, and has compiled a 98-76 record with a 3.22 earned run average over 238 starts since breaking into the majors as a 19-year-old with Seattle in 2005.
"King Felix" topped the AL with a career-high 19 victories in 2009, then claimed his first career Cy Young the following season after going 13-12 with a league-best 2.27 ERA along with 232 strikeouts.
02/12 16:04:29 ET