Pitcher Bronson Arroyo said from his vantage point he thought DeJesus was safe.
"It was a tough loss," Boston first baseman Kevin Millar said. "We should have found a way to win this game."
It was only Boston's second loss in six extra-inning games. Had it not been for the offensive heroics of DeJesus and a superior defensive play by left fielder Terrence Long in the seventh, the Red Sox wouldn't have been forced to work overtime.
The Red Sox were cruising with a 3-1 lead in the fifth behind Matt Clement and feeling good about seeing Millar deliver a second-inning homer, his first in 182 at-bats. But DeJesus launched a two-run homer deep into the right-field bullpen to tie it. DeJesus reached on his last five trips to the plate.
Boston had a chance to jump back on top in the seventh when Varitek fanned on a 3-2 pitch with the bases loaded and one out. Millar then smoked a sinking liner to left and Long laid out and made a diving catch to prevent two runs.
"Terrence Long made a great play," Millar said. "It was just one of those nights. Everybody in their bullpen throws 95 mph. That's Kansas City's strength. They have great arms out there and we have to do a better job in finding a way to get a run across."
The Red Sox left 13 men on base, as did the Royals. Boston was 2-for-10 with runners in scoring position, hit into a couple of double plays and didn't score over the final eight innings.
"We had opportunities to spread that game out and didn't do it," manager Terry Francona said. "When the game went to extra innings, the Red Sox had to call on Arroyo for relief duty.
"Bronson knew when the game started he was available to pitch," Francona said. "He'll be available [to start] on Saturday. We'll be fine."
Arroyo got through the 10th inning in good shape. But in the 11th, DeJesus drew a one-out walk and Long singled to left. Mike Sweeney drew a walk as Arroyo pitched carefully to Kansas City's most noted hitter. That meant Boston had to bring the outfield in and draw the infield up close as Ambres stepped in.
Arroyo worked the count to 2-2 before Ambres got enough wood on the ball to produce the sacrifice fly.
"I didn't want to go full count and have a chance of losing the game on a walk," Arroyo said. "So I threw him a breaking ball right down the middle of the plate and took a little off. He popped it up."
But the popup was just deep enough to get the winning run home and keep Boston's lead over the Yankees at 3 1/2 games in the American League East.
"I had a great first inning and felt good in the second inning," Arroyo said. "But Long hit an unbelievable ball down and away for a single that gave them a runner in scoring position. Then I had to pitch very carefully to Sweeney."
The loss means Boston (72-52) can't go home with a winning road trip on its 10-game swing. The Red Sox will try for a 5-5 split on Thursday night as Curt Schilling returns to the rotation.
"Tough game to lose," Francona said.
The 41-83 Royals know the feeling all too well. For most of the year, they've been where the Red Sox were late Wednesday night.