KANSAS CITY -- The Yankees' plan to continue using their fifth starter, which means that Kei Igawa could have one more chance to impress. He didn't take advantage Thursday.

With top prospect Phil Hughes gaining steam in his rehab and nearing a projected return, Igawa struggled yet again, allowing five runs to the Kansas City Royals as the Yankees fell Thursday at Kauffman Stadium, 7-0, ending a six-game winning streak.

"I haven't been able to make gains, and that's very frustrating," Igawa said. "I have to look at this and move forward."

Alex Rodriguez went homereless, remaining at No. 499 for his career.

Igawa has a 6.79 ERA in 11 starts and one relief appearance for the Yankees, and said that a major part of his struggles has stemmed from not learning hitters quickly enough.

A $46 million investment who signed a five-year deal with the Yankees in January, Igawa's progression has been slow. Though he shows flashes of confidence and competence, he also runs into rocky patches that seem to undo all the good he exhibits.

"It's teasing," said Yankees manager Joe Torre. "You know he's trying and working hard at it. He's very serious-minded about what he does. He pitches well enough to think it's coming, and something just gets out of hand. That's the tough part."

Igawa, who would next start Wednesday vs. Chicago, was hurt most by a four-run second inning. The frame featured hanging pitches that became RBI triples to Mark Grudzielanek and Tony Pena Jr., plus a two-run double by center fielder David DeJesus.

The Royals sent eight men to the plate in the inning against Igawa, who also surrendered an RBI double to Pena in the fifth on what was the left-hander's 102nd and final pitch.

"He's missing some spots," Torre said. "I thought he settled in a little bit better, but I still think -- even though I think he improved -- it's all about command. His stuff is good; he just needs to command it. I still think he's going forward."

Igawa walked two and struck out five, hitting a batter and throwing a wild pitch. Returning from a strained left hamstring and a sprained left ankle, Hughes made his fifth rehab start for Triple-A Scranton/Wilkes-Barre on Monday, throwing six scoreless innings, but Torre said the organization is leaning toward having Hughes make one more start in the Minor Leagues.

"It's what [player development] people are comfortable with," Torre said. "If that's the case, that's it. Those are the people that see him, and I think it's important to stay with that, especially this close to his being ready."

Reliever Sean Henn, the Yankees' 13th pitcher and a likely candidate to be sent back to Triple-A when the club adds a position player, allowed an RBI double to Billy Butler in the seventh and Alex Gordon's seventh home run, a solo shot, in the eighth.

The Yankees couldn't muster much against Royals starter Jorge De La Rosa, who scattered six hits over 5 1/3 innings before yielding a jam to reliever Zack Greinke, who escaped by coaxing Jose Molina to ground into a double play.

De La Rosa surrendered Rodriguez's 400th home run June 8, 2005, while pitching for the Brewers. With Rodriguez now sitting on 499, thousands of flashbulbs accompanied Rodriguez's first at-bat and seemed to indicate that a sellout crowd of 37,036 expected to witness even more history.

"Honestly, it's remarkable," Rodriguez said. "I wasn't even thinking about it. I don't even think about it at all, except that first at-bat. I've never seen more flashbulbs in one of my at-bats."

The Royals had other ideas for Rodriguez, who went 0-for-2 and was hit by an errant curveball on his back foot. Kansas City elected to walk Rodriguez with first and second bases open and two outs, pitching to Hideki Matsui instead. Matsui popped out to end the inning, and A-Rod said that he did not believe the maneuver had anything to do with stopping a chance at hitting No. 500.

"[Royals manager] Buddy Bell is a great baseball man and he wants to win a game," Rodriguez said. "He thought the best way to win a game was to put me on base."

The strategy worked, and the trend would be a lingering one for the Yankees, who fared 0-for-12 with runners in scoring position, including Matsui also grounding out with the bases loaded in the fifth.

"We got [De La Rosa's] pitch count up early enough, and when we had the opportunity to do some damage, he was better than we were," Torre said.

Playing his first game after being traded by the Angels on Saturday, catcher Molina had hits in his first two at-bats but grounded into the inning-ending double play in the sixth, wasting a two-on, one-out opportunity.

The Yankees were also done in by the son of one of their own, as first-base coach Tony Pena watched his son stroke a double and triple with two RBIs and a run scored for Kansas City. Torre said that he knew Pena was "smiling on the inside, but he's not allowed to do it on the outside."

"It was fun to see him play, I want you to know that," Pena said. "To see the way he goes out, the attitude he brings to the field ... I was very impressed."

The younger Pena also achieved a milestone of sorts in the eighth inning when he worked a walk off Henn, the 26-year-old's first walk in 244 plate appearances since May 5 vs. Detroit.

"I really don't worry about walks, because I didn't walk either," the elder Pena said. "We didn't walk off the island."

The Yankees have won 12 of 16 since the All-Star break, but fell 7 1/2 games off the American League East pace with Boston's victory at Cleveland on Thursday. New York remains 4 1/2 back of the Indians in the AL Wild Card race.