"I was kind of taken back by it," Hairston said. "His first pitch was behind me. From the box, it looked like he was throwing at me, but you'd have to ask him."
But a brief confrontation between Hairston and Mesa in the eighth inning added a little excitement to a game dominated by Wood and the Cubs.
Hairston and Mesa exchanged words after the Cubs center fielder was retired in the eighth inning by the Pirates closer.
Mesa took a couple of steps off the mound as Hairston ran by him and toward the dugout. Mesa kept jabbering and was eventually thrown out of the game by umpire Gary Darling.
Mesa didn't comment after the game, the Pirates' third consecutive loss.
"The umpire explained to me that (Mesa) charged off the mound," Pittsburgh manager Lloyd McClendon said. "I told him that was absolutely not the case.
"When I played the game, if I thought somebody threw at me, I told him about it and charged the mound. I certainly didn't pop up and then walk back across the mound and say something. That's not the way to handle it. If you think he threw at you, then go get him."
Hairston, who has just 30 career homers, said he was "frustrated and upset."
Wood said, "I think it was just two guys letting the testosterone take over."
Three Cubs relievers pitched three scoreless innings of relief after Hairston's grand slam in the sixth made it 11-1.
"It felt good, not because it was a grand slam," said Hairston, who was 0-for-6 before the home run. "I think it was the first hit I had since the (All-Star) break. It felt good to contribute."
Aramis Ramirez hit his 20th homer, a three-run shot, in the Cubs' fifth win in a row. During the streak, they've scored 42 runs.
Every player in the Cubs' starting lineup had at least one hit as Chicago collected 16 against five Pittsburgh pitchers.
Wood (3-2) made his fourth start since spending nearly two months on the disabled list with a sore shoulder. He struck out five and walked none in throwing 75 pitches.
Cubs manager Dusty Baker said he lifted Wood after the right-hander sat in the dugout after Chicago had batted around and scored five runs in the sixth.
"It was a long inning and we're still cautious with him," Baker said. "We had a lot of runs and figure that was enough. With all the runs, we figured six (innings) was good."
Wood appreciated the offensive support and didn't mind leaving.
"It's nice to get a 10-run lead and have the opportunity to keep it under around 80 pitches today," he said. "The more innings you can save the better.
"I'm just trying to repeat the same delivery and repeat quality pitches," he added. "I was moving the ball in and out and up and down. I'm getting ahead of guys and just trying to throw in the strike zone."
Pittsburgh's Jose Castillo had three of the team's four hits -- including a solo home run in the second. After allowing that homer, Wood retired eight in a row and 14 of 15.
Neifi Perez drove in two runs with a single and a double as Chicago climbed above .500 at 45-44. Wood drove in his first two runs this season with a double in the second.
Pittsburgh starter Josh Fogg (4-5) lasted just four innings, yielding six runs on seven hits. He hasn't won since June 1, a span of eight starts.
Ramirez's three-run shot to left in the third extended Chicago's lead to 6-1.
Perez doubled in a run to launch the Cubs' five-run sixth. With one out and the bases loaded, Hairston lined his grand slam off the left-field foul pole.
- Both of Wood's hits this season are doubles.
- Ramirez has hit 20 or more homers in four of his five full major-league seasons.
- Perez has eight hits in his last 16 at-bats.
- Fogg's four-inning outing tied his shortest of the season.
- Dallas Mavericks owner Mark Cuban, a Pittsburgh native, led the crowd in singing "Take Me Out To The Ballgame" during the seventh-inning stretch.
- Raul of Real Madrid threw out the ceremonial first pitch. The Spanish soccer club meets Chivas Guadalajara in a match in Chicago on Saturday.