Moments later, he received a visit from third baseman Kevin Youkilis.
"You can't do that anymore," said Youkilis, warning Green that he could be called for a ball if he continued going to his mouth.
"You can do that in high school, but you can't do that here."
Green has played 78 games at shortstop this season, seven each at second and third base and three in left field. So he followed his teammate's advice, then fired a scoreless eighth and ninth inning to mop up the Red Sox's 9-5 loss to the White Sox.
On a night when Boston received just four innings from starter Junichi Tazawa, who was tagged for nine runs on 10 hits, manager Terry Francona called on the utility man to save the bullpen.
As his nearly unblemished line score would indicate, Green delivered.
"I didn't really want to do it, but I understood the situation," said Green, the first Red Sox position player to pitch multiple innings in a game since Dave McCarty in 2004. "That's why I said, 'OK, I'll go out there and try to have fun.'"
Green seemed to have quite a bit of fun on the hill, allowing nothing more than a trio of walks while facing nine hitters over two frames.
"I just wanted to throw strikes," Green said. "I didn't know my ball was going to move all over the place. I told Tito, 'I might get hit, I don't know.' I didn't know what to expect. I hadn't thrown to a catcher in 11 years."
After learning of his unique assignment in the third inning, Green warmed up in the batting cage behind the Red Sox's dugout with outfielder Rocco Baldelli, who pronounced the hurler ready to go soon after.
Green knew he'd pitch the eighth. But the ninth too? Not exactly.
"That first inning I didn't really have a choice," Green said. "[Francona] told me the way it was going to work, with Manny [Delcarmen] pitching two [innings] and Ramon [Ramirez] pitching one [inning], and then I come in. But I asked [pitching coach John] Farrell, 'Who's going to pitch the ninth?'
"It worked out, and it was kind of fun, too."
Green joined Jonathan Van Every (April 30 at Tampa Bay) as the second Red Sox position player to pitch in a game this season. Only once before in club history have two different position players pitched during the same season: Doug Taitt and Jack Rothrock in 1928.
Earlier Thursday, the Red Sox released right-hander Brad Penny to make room for lefty reliever Billy Wagner, obtained Tuesday from the Mets. But Wagner had a bullpen session Thursday and was unavailable for the game.
The scoreless appearance earned Green rave reviews from his teammates.
"He was doing his best out there," catcher Victor Martinez said. "He was just trying to throw the ball over the plate, and he did great. Obviously he was a little wild, but you have to expect that when you come into a game and face good hitters."
"He's probably got the best arm on the team," Youkilis said. "As a position player, he just came in and threw the ball. He did a good job. It's pretty cool that he came out with a zero ERA."
John Barone is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.