Thomas became the 21st player to reach 500 homers Thursday with a three-run shot in the first inning, but the Blue Jays (39-39) lost 8-5 to Minnesota.
The two-time AL MVP also tied his season high with four RBIs, but was ejected in the ninth inning after being called out on strikes for the second time.
“Now that I’m healthy again I would love to get to 600,” he said. “It’ll take a lot of luck to get there, but I really got to have a strong second half and really prove that I can still play this game.”
The 39-year-old Thomas has five home runs in his last 11 games, and 13 this season.
Thomas’ 12th home run came in McGowan’s last start, but the right-hander didn’t need much help, allowing a leadoff single in the ninth that ruined a no-hit bid in Toronto’s 5-0 win over Colorado on Sunday.
It was the only hit allowed by McGowan (4-3, 4.83 ERA), who settled for his first complete game in 20 major league starts. This is his first season as a full-time starter.
McGowan is making his first start against the Mariners (42-33), but he allowed two hits and struck out four in 3 2-3 scoreless innings during two relief appearances against them in 2005.
McGowan was hit hard in his outing prior to Sunday’s, allowing six runs and eight hits in a season-low 1 2-3 innings against the Dodgers on June 19.
The Mariners will counter with Jarrod Washburn (6-6, 4.09 ERA), who won his last start to begin the team’s current five-game winning streak. It was one of the best performances of the season for the left-hander, who allowed one run and seven hits while striking out five in eight innings to beat Cincinnati 9-1 on Saturday night.
Washburn is 1-6 with a 4.60 ERA in seven starts against Toronto. He has lost five straight starts against the Blue Jays, posting a 5.04 ERA.
Seattle had an off day after extending its winning streak with a 2-1 win in 11 innings over Boston on Wednesday. Ichiro Suzuki scored on Jose Lopez’s double to give the Mariners a three-game sweep of the AL East-leading Red Sox.
Suzuki continues to come up big in the field, too, recording a career-high 11 putouts in center field Wednesday.
“I figured we had a day off … so I have no problem with it,” Suzuki said of his effort in the field.
Suzuki, who has won six straight Gold Gloves for his play in right field, leads the majors with 227 putouts and has not committed an error.
Seattle has won seven of eight following a six-game losing streak.
This will be the first meeting between Seattle and Toronto since last year, when the Blue Jays won five of the teams’ nine matchups.