Don't throw Grant Green the same pitch twice. Especially not the "new" Grant Green.

Green crushed a grand slam in the fifth inning Thursday, part of a seven-run comeback that fell just short as the Phoenix Desert Dogs suffered a 10-8 loss to the Mesa Solar Sox in the Arizona Fall League.

For MLB.com's top A's prospect, who's worked on overhauling his swing this fall, it was another game to file away in his goal of becoming a better power hitter.

"In the at-bat before, he beat me with a fastball in," Green said of his battle with Mesa's Nathan Baker (Pirates) in the fourth. "I knew he'd try to go there again. He ended up throwing another fastball straight in, and I finally got the bat head out and pulled it."

Green's fourth homer made it a 7-5 game. Phoenix fell into a 7-0 hole by the third after starter Murphy Smith (Athletics) was charged with all seven runs on 10 hits and a pair of walks over 2 1/3 innings.

After rallying to tie the game in the eighth, 8-8, Mesa pulled away in the bottom of that frame on a two-run homer by Brian Dozier (Twins). Xavier Avery (Orioles), the Solar Sox's leadoff hitter, went 4-for-5 and fell a homer shy of the cycle for Mesa.

"Any loss is tough, especially since we we're down 7-0 going into the fourth. So coming back from that, it ended up it didn't go our way today," said Green, who was the No. 13 overall pick in the '09 Draft. "Their guy hit a bomb in the eighth, but it was tough. We'll come back tomorrow and do it again."

Green spoke earlier this fall about his work with Phoenix manager Todd Steverson, who is also the hitting coach at Triple-A Sacramento, an A's affiliate. Steverson saw Green's swing earlier in the year and approached both the outfielder and Oakland's player development brass about some tweaks.

So far, even Green admits the adjustments have paid off.

"We completely changed my swing," said Green, a USC product who earned a first-round selection in 2009 and hit .291 at Double-A Midland this year with his "old" swing.

"He told me from day one, 'We're going to work on a new swing, get a little more load, a leg kick and generate some more power,'" Green said. "It's worked, I've definitely improved. And I'm doing it against better pitching as well."

Green, who went 2-for-5 and hit second Thursday, is batting .308 with four homers and 17 RBIs in 22 games for Phoenix after slugging nine homers in 127 Texas League games.

"Right now," he said, "it's easy to see that it's working. I just need to stick with it. The more and more I work, the more power I'll show."

Still, it took agreement across the board with the A's to entrust Steverson with the swing of the organization's top hitting prospect. Green said he was approached about it after this Minor League season ended, a campaign in which he had 33 doubles, 62 RBIs, went to the Futures Game and earned Texas League All-Star honors twice.

"He saw my swing in Sacramento and he saw a lot of holes with it," said Green, who hit .318 in 2010 and .316 in '09, both at Class A Advanced Stockton. "He talked to our roving hitting guy at the time, and he talked to upper management people and asked if he could work with me."

Green said his stance has been changed along with his timing to the ball. He's hit in eight of his last 10 games, plating 10 runs in that span.

"He thought I was too narrow with my stance, so we widened it. He thought I was static with my load. He said we're trying to generate power. ... It's easy to see that it's working so far."

So should Oakland fans expect to see the top pick in the Bay Area this summer? Or perhaps even this spring? Green hopes he gets a chance to show off his new mechanics when the time comes.

"Hopefully I get a big league invite and do that again," he said. "But it's the same thing as the last two years, impress the coaches, get as much tutelage as possible, pick the brains of the vets, see what they do and just increase my game that much more. If the power there, awesome."