The shortstop who went to spring training as a non-roster player but is now the starter hit the first pitch in the bottom of the ninth just inside the right-field foul pole 302 feet from home plate.
"I didn't even comprehend the fact that I swung at the first pitch and it was a walk-off" homer, he said after a 6-5 win over the Atlanta Braves on a windy, misty afternoon. "I hit second base and everybody is standing at home plate and then I realized what was going on."
His jubilant teammates had poured out of the dugout when he hit Jeff Bennett's first pitch of the game for his fourth homer. They mobbed him when he reached the plate.
"He's really done a good job," Boston manager Terry Francona said. "It's gotten to the point where he's just been a really good player, not a really good non-roster player, a really good major league player."
Not bad for a 30-year-old who had just one full season in the majors in his 10-year pro career before this season.
"I thought I hit it decent to right field but I thought it was going to be an out because the wind was so bad," Green said. "Fortunately, it was blowing to right and the wind blew it right where it needed to go."
The Braves rallied twice to tie the game.
"We did everything but win," Atlanta manager Bobby Cox said. "We had more line shots than we did all year long, at people, with men on, too."
In the seventh, Atlanta scored twice to tie the game at 4. Singles by Anderson, Martin Prado and Gregor Blanco produced one run. Ramon Ramirez replaced starter Tim Wakefield and allowed a tying single to Nate McLouth.
J.D. Drew gave Boston a short-lived 5-4 lead with an RBI single in the seventh one pitch after he took a pitch that appeared to be over the plate for a third strike. Cox came out of the dugout, argued and was thrown out by plate umpire Bill Hohn. So were pitcher Eric O'Flaherty and third baseman Chipper Jones.
It was the major league-leading 145th ejection for Cox and his second of the year. Hall of Famer John McGraw is second with 131.
"It was a ball that was right down the middle for strike three. It was obvious," Cox said. "He blew the call and it upsets guys when it costs you games. And it cost us the ballgame."
Dustin Pedroia doubled and took third on an error when Jurrjens bobbled Kevin Youkilis' grounder. Jason Bay hit a sacrifice fly and David Ortiz gave the Red Sox a 3-2 lead with his sixth homer of the season, a two-run shot.
A misplay that fell for a hit in the fourth led to Boston's fourth run.
Ortiz led off with a pop fly. Shortstop Yunel Escobar and Jones looked at each other and the ball dropped between them with neither touching it.
"It was a strong wind blowing. I just assumed that he was going to take it," Jones said. "It ended up costing us a run."
Wakefield missed a chance to join Toronto's Roy Halladay and Minnesota's Kevin Slowey as the only two 10-game winners in the majors. ... Jurrjens allowed two earned runs in 6 1/3 innings. He is 0-3 in his last four starts since his most recent win, May 29 at Arizona. ... Boston 3B Mike Lowell got his second straight day off before the Red Sox are off Monday. Lowell, who had offseason hip surgery, has played in 65 of the team's 69 games. ... Ortiz has 295 homers and 999 RBIs in his career. ... Anderson was 6 for 10 with a double and five RBIs in the three-game series.