"I'm a little bit disappointed, because I think a lot of the fans were looking for me to keep on winning," Tanaka said through an interpreter. "Next time out, I'll try to get a win again and try to keep it going again."
Tanaka had not lost a regular-season game in 42 starts. He did lose Game 6 of last year's Japan Series before returning to get the save in Game 7, but Tanaka's last regular-season defeat came on Aug. 19, 2012, when the Seibu Lions beat Tanaka's Rakuten Golden Eagles.
"It's quite an accomplishment," Yankees pitching coach Larry Rothschild said. "He doesn't like to lose, no matter if he's going 30 games in a row or whatever. He doesn't take kindly to losing."
Tanaka's first big league loss came against the Cubs, a team that made a serious bid to acquire his services this past offseason. The Cubs made a strong offer, reported to be six years and $120 million, which was bested by the Yankees' seven-year, $155 million offer.
Owning the worst record in the Majors entering play on Tuesday, they instead settled for playing spoiler to Tanaka's streak.
"We really executed," Cubs catcher John Baker said. "Maybe [unbeaten boxer] Floyd Mayweather may lose now. We beat the Mayweather of baseball today. Hopefully we can sprint forward from that."
The first team to face Tanaka multiple times in his brief big league career, the Cubs stroked eight hits -- three off the bat of Luis Valbuena, two of them doubles -- as Tanaka struggled with his command on a rainy night at Wrigley.
"If he has his good splitter tonight, I think he gives a much better performance," Yankees manager Joe Girardi said. "Since it's the first time he saw a team twice and they scored four runs, people are probably going to make a big deal out of it. ... I wouldn't make too much of it."
Mike Olt had three RBIs for the Cubs, who squeezed a decent outing from starter Jason Hammel -- a veteran with American League experience who may just have been auditioning to step in as a trade target for the Yankees later in the summer.
Tanaka said that he knew his stuff was off in the bullpen, and he struggled with his command in the strike zone, responsible for the great departure from the form that allowed him to limit the Cubs to a pair of bunt hits over eight dominant frames on April 16 at Yankee Stadium.
"I don't think it's just the splitter. I think it goes for all of my pitches today," Tanaka said. "I don't think I was able to command my pitches the way I wanted to. If I knew why I wasn't able to do that, then I'll be able to adjust it during the game."
Hammel limited the Yankees to a run on four hits over 5 2/3 innings, with Mark Teixeira stroking a sixth-inning RBI single. Hammel left with two men on in the sixth, but Justin Grimm got Alfonso Soriano to bounce into an inning-ending fielder's choice.
"It seems like we barreled some balls, but we just hit them up," Girardi said. "It seemed like we just missed. He's got good movement. We've seen him very good with Baltimore the last few years."
Emilio Bonifacio's third-inning single drove home Baker with the Cubs' first run. Valbuena doubled and scored on an Olt single in the fourth inning, giving the Cubs a two-run lead.
Chicago might have dented Tanaka for more in the fourth, but the Cubs attempted two bunts with runners at third base. Tanaka fielded both, deftly shoveling a Hammel attempt to catcher Brian McCann to catch Olt for the second out of the inning.
He then essentially repeated the play as Bonifacio's bunt led to Baker getting nabbed at the plate.
A pair of sixth-inning sacrifice flies allowed the Cubs to pad their lead against Tanaka, who walked one and struck out seven in an 88-pitch outing. Those fly balls were lifted by Olt and Baker, with Teixeira throwing a ball into center field and extending an inning in which Tanaka asked the grounds crew to tend to a soggy mound.
"I can't make the weather my excuse," Tanaka said. "I think it's my first time that it rained since I came here, but that happens. I need to be able to adjust to that."
The Cubs added two seventh-inning runs. Bonifacio tripled to open the inning against Preston Claiborne, trotting home on Starlin Castro's one-out bloop single to center field. Matt Daley also issued a bases-loaded walk to Olt, forcing home the sixth Cubs run.
New York pieced together a ninth-inning rally, loading the bases for Derek Jeter, who was honored in a pregame ceremony and received a No. 2 from Wrigley Field's iconic manual scoreboard. The Yankees' captain grounded out to end the game.
Girardi said that despite the injury-riddled state of the Yankees' rotation, he rejects the idea that losses in Tanaka's starts are somehow magnified.
"I don't think it's fair to him, and I don't think it's fair to the rest of the guys," Girardi said. "Everyone has to contribute. If we're going to get where we want to be, everyone has to contribute. You can't expect one guy to take you to that spot."