But it wasn't until after his opposite-field solo shot in the third inning of the Rockies' 9-4 victory at AT&T Park on Tuesday night that he learned how special his swing was.
Left field at AT&T Park is one of the toughest places to hit a home run, especially for a left-hander not named Barry Bonds.
"I hadn't heard, but afterwards they told me," said Smith, who also doubled and had an RBI single. "It probably won't happen again."
Smith, a pinch-hit darling of last year's playoff run, is getting plenty of chances for big games these days for the struggling 2008 Rockies, whose victory prevented the Giants from tying them for third in the National League West.
Smith came through the Minors as a muscular corner outfielder. The Rockies wanted to try him in center this spring, but he reported to camp too big to attempt such a transition. However, Smith hit .323 with 10 home runs at Triple-A Colorado Springs, trimmed down and earned a callup.
Now the club is wondering if Willy Taveras, who leads Major League Baseball in steals but has slumped with the bat, is the answer in center and atop the lineup. So Smith has had five starts in center.
"He's able to get in a little bit of a rhythm," Rockies manager Clint Hurdle said. "He faced a very good right-handed pitcher tonight, and obviously he squared a couple of balls up, big-time."
Smith said, "Nobody wants to come up here and be a pinch-hitter, but you try to the best you can in whatever role you're in. But definitely starting games is fun."
Smith's homer, his fourth in the Majors, cut the Giants' lead to 3-2. The Rockies would add two in the fourth. Smith was robbed of RBIs when his drive to deep right-center bounced over the wall for a ground-rule double, meaning Omar Quintanilla couldn't score from first. Troy Tulowitzki's single that eluded third baseman Rich Aurilia drove in both runners.
The Aurilia play was originally ruled an error but was changed after the game. However, the Giants said they are appealing the change. After the ruling was changed, Lincecum's ERA went from 2.51 to 2.66. The change meant the Mets' Johan Santana became the NL's ERA leader at 2.64.
Lincecum, who struck out nine but gave up six runs, six hits and five walks, left with two on and one out in the fifth. Joe Koshansky, another callup, greeted Keiichi Yabu with a two-run double. Smith singled home a run in the fifth.
Tulowitzki would knock a sixth-inning solo shot off Osiris Matos and match his career high for hits in a game by going 4-for-5.
Rockies starter Ubaldo Jimenez (12-12) gave up four hits and all three runs off him came in the second inning, but he lasted six innings, with four hits, four walks and four strikeouts.
"At first, my fastball command wasn't there," Jimenez said. "But after the third inning everything improved."
Thomas Harding is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.