Semien hit his 32nd home run and reached base six times, and the A's routed the Texas Rangers 12-3 on Saturday night to maintain their two-game lead in the AL wild card race.
"It is not premature to talk about him in the MVP race," Melvin said. "You don't have to knock in 100 runs to be an MVP, especially in the leadoff spot. I don't know that anybody's been more important to a team than Marcus has."
Sean Manaea allowed two runs over 5 2/3 innings after being staked to a big lead early to win his third straight. Matt Chapman drove in two runs and had two hits, both coming as part of a seven-run first inning.
Mark Canha also went deep and scored three times as Oakland won its fourth straight.
The A's (94-61) lead Tampa Bay (92-63) in the chase for the top AL wild card. The Rays beat Boston on a walkoff home run in the 11th inning earlier Saturday.
"I look at the scoreboard every inning," Semien said. "The Rays are tough. They fought to the end last night and tonight."
Semien singled in the first, homered in the fifth and singled in the seventh to go with three walks. He's the first A's player to reach base six times since Olson did it April 18, 2018.
Semien is 19 hits shy of becoming the first Oakland player to have 200 hits since Miguel Tejada in 2002.
"It's definitely not a goal I set out for myself," Semien said. "I never thought I would ever get close to that."
Oakland also got another encouraging start from Manaea.
Sporting corn rows as part of his ever-changing hairstyle, Manaea (3-0) took a shutout into the sixth inning before giving up a pair of solo home runs to Elvis Andrus and Danny Santana that raised the lefty's ERA to 1.14.
Manaea walked one and struck out four in his fourth start since returning from a year-long absence following shoulder surgery. That followed back-to-back shutouts by the A's, whose rotation has been stellar as of late. Since Aug. 14, Oakland starters are 17-2.
Nick Solak homered for the Rangers. Texas lost its seventh straight against Oakland.
"It's tough when you're down 7-0 to start the game," manager Chris Woodward said. "We've got to do a better job of giving our offense a chance."
Rangers starter Brock Burke (0-2) failed to make it out of the first.
Matt Olson started the onslaught with an RBI single. After a throwing error by third baseman Solak allowed another run in, Ramon Laureano doubled down the first base line to make it 3-0.
Sheldon Neuse added a sacrifice fly, Josh Phegley drove in a run to end Burke's night, and Matt Chapman -- who singled earlier in the inning -- knocked in two with a single off reliever Luke Farrell.
SCORELESS STREAK ENDS
Oakland pitchers had not allowed a run in 29 consecutive innings before Andrus' home run leading off the sixth. The scoreless streak is tied for the second-longest in Oakland history and is the team's longest since a 29-inning stretch in 1996.
ALL F'S AGAINST OAKLAND
Burke allowed 13 runs in 3 2/3 innings (31.88 ERA) over two starts against the A's this season.
A'S LEGENDS HONORED
Former Oakland manager Tony La Russa, franchise home run leader Mark McGwire, ex-Cy Young winner Vida Blue, shortstop Bert Campaneris and former owner Walter Haas Jr. were inducted into the A's Hall of Fame during a pregame ceremony. The five were joined on the field by previous inductees including Rickey Henderson, Dennis Eckersley, Dave Stewart and Rollie Fingers.
Athletics: Laureano was pulled from the game two innings after making a sliding, tumbling catch in the Rangers bullpen.
Oakland's Tanner Roark (10-8, 4.12 ERA) is 4-1 since being acquired from Cincinnati at the deadline, but the right-hander is winless in three career starts against the Rangers. Texas RHP Lance Lynn (14-11, 3.77) is winless over his last eight starts. Lynn needs to pitch 4 1/3 innings to reach 200 for the third time in his career.
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Semien, Canha homers help A's rout Rangers
Marcus Semien and Mark Canha each hit solo home runs in the Athletics' 12-3 win vs. the Rangers.