Sosa connected for his 600th career home run with two outs in the fifth inning of the Texas Rangers' 7-3 victory over Marquis and the Cubs.
"It was a cutter, I just left it up in the zone, and he put a good swing on it," Marquis said of the 1-2 pitch that landed in the Rangers' bullpen for the milestone homer.
"He hit the ball on the ground like I wanted him to," Marquis said of Sosa's first two at-bats, in the first and third innings. "I beat him with my sinker in. I went away from my strength, and he made me pay for it."
How coincidental was it that Marquis was wearing Sosa's No. 21? Anyone who saw any of Sosa's franchise-record 545 homers with the Cubs recognized his trademark hop as he left the batter's box and his heart-tapping, kiss-blowing salute as he crossed home plate.
Marquis was the 364th different pitcher to serve up a homer to Sosa. It didn't matter to the right-hander, who was just beginning his career in 1998 at Class A Danville when Sosa was belting a club-record 66 homers that season for the Cubs.
"Other than the fact that it cost us losing the game, other than that, it really doesn't matter," Marquis said of his place in the history books.
Sosa the fifth player to hit 600 long balls, joining Hank Aaron, Barry Bonds, Babe Ruth and Willie Mays.
"The home run is probably the most revered stat in baseball, for whatever reason," Cubs manager Lou Piniella said. "You hit 600 of them, you've trotted around the bases a long, long time."
It was not a night Marquis would like to remember. He lost his third straight decision, and gave up six runs -- four earned -- on five hits and four walks over five innings. He hasn't won since May 9. Frank Catalanotto made matters worse after Sosa's blast when he connected on his fifth home run. While Sosa has hit 600 homers, Marquis has served up 139.
"It was exciting to see history being made in any sport, for that matter, any part of life," Marquis said. "He's been a great player for a long time, and he's having a great year after missing a year.
"Congratulations to him, but I still have to do a better job of making better pitches there, to him and everybody else in the lineup," Marquis said.
The right-hander got off to a bad start, walking the first two batters he faced. Both eventually scored. Piniella sent pitching coach Larry Rothschild to the mound to talk to Marquis and figure out what was wrong. He just couldn't get comfortable.
"It was a good moment," Piniella said. "He's done something not too many players have done. He should be proud of it. I congratulated him. I wish he had done it in a losing effort, but it's a tremendous feat and he should enjoy the moment.
"You like to see professionals do what they do," Piniella said. "Sammy's been a good hitter all these years, and he's hit with a lot of power. You respect that."
"He's hit a lot of home runs," Piniella said. "Six hundred is a big number."
Sosa is the Cubs' all-time home run leader, hitting 545 while with the team. Now he has 600, and he did so with his first career blast against the Cubs. Alfonso Soriano also homered in the game, but he's at 220 in his career and has a long way to go to catch up to Sosa.
"I'm very excited for him," Soriano said. "I think he deserves it. There's not too many people in this game who can hit 600 home runs."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.