Greggersen, who was wearing a necklace with a syringe dangling from it, said Bonds hadn't given him an autograph during a long-ago Spring Training game. Bonds traditionally carries baseball cards with an autograph etched across his image and passes them out during games.
Greggersen also said the unmarked tube had a sports gel in it, not toothpaste. Bonds pointed the object out to a security guard, who retrieved it from the grass behind him.
Bonds, who was 1-for-3 with two intentional walks before coming out of the game for a pinch-runner in the eighth inning, told MLB.com he didn't want to talk about the incident. He also didn't make himself available to the media after the game, the Giants' eighth win in their first 12 contests.
Bonds continues to struggle. He is homerless and is batting .192 (5-for-25) with two doubles, four runs scored, one run batted in and 13 walks and has been hit by pitches twice. If he doesn't homer Tuesday night against the Diamondbacks in the team's 13th game of the season, Bonds will have matched the longest homerless streak to open a season of his now 21-year career.
Bonds homered in the 13th game of the 1998 season. That year, it was also the 13th game he had played in. This season, he has played in 10 of the Giants' first 12 games and is expected to be in the lineup Tuesday night.
He's currently stuck at 708 career homers, six behind Babe Ruth's 714 and 47 short of Hank Aaron's all-time record of 755. Bonds hasn't hit a homer since this past Sept. 27.
Monday night was the second time during the Giants' first two road trips that a fan has thrown an object toward Bonds on the field. On Opening Night in San Diego, Bonds picked up an oversized syringe with his fielding glove as he crossed the foul line walking toward the dugout in the eighth inning.
The Padres, using the feeds from video security cameras, searched the stands behind the third-base dugout at PETCO Park in the days after the game, but to no avail. No one was arrested for the incident.
On Monday night, local security at Chase Field descended on Greggersen almost immediately.
"We take that stuff very seriously," Diamondbacks President Richard H. Dozer told the Associated Press. "We had three guys on [the fan] before the follow-up was through."
Major League Baseball has also taken security issues surrounding Bonds very seriously this season. Fans, on the road particularly, have been loud and abusive, although the 21,610 in attendance Monday were relatively calm in comparison to the three-game weekend series in Los Angeles.
Thus far, MLB has had top members of its security team on location supervising at each venue the Giants have played. Dozier said the Diamondbacks beefed up security for the four-game series.
"They might be doing a good job, we don't know," Giants manager Felipe Alou said. "It's hard to control everything and everybody."