It helped set the foundation for two World Series championships in three years, delivering in Buster Posey and Brandon Crawford a pair of players who would become among the game's best.
"Buster and I signed a day apart and went to Arizona the same time, then played [in the Minors] together," said Crawford, a fourth-round pick after Posey was taken No. 5 overall in the first round. "He's one of my better friends on the team. It worked out well for all of us -- including John Barr."
In his 29th season in the game, having started as a scout with the Mets in 1984, Barr now answers to the extended title of vice president and assistant general manager in charge of scouting and international operations.
While he has been studying amateur talent with the eye of a diamond appraiser for three decades, Barr understands it's rare that everything falls into place the way it did in 2008.
No player from that Draft has produced on Posey's level. If they held it all over again, Posey would go first and Crawford would be a high first-rounder.
As an added benefit, Posey and Crawford deftly handle the two most important roles on the field apart from the mound. Giants manager Bruce Bochy is in good hands with Posey behind the plate and Crawford at shortstop.
Both are 26, just coming into their prime years. In addition to their physical skills, they share an intuitive sense of doing the right thing that qualifies as a sixth tool in the scout's notebook.
"Needless to say," Barr said, "we feel very fortunate to have Buster and Brandon. They're terrific players and great teammates."
Posey, the 2012 National League batting champion, is hitting .307 with seven homers and 31 RBIs. He's the leading vote-getter in the NL for the All-Star Game in New York's Citi Field.
Crawford, a regular on the highlight shows with his spectacular glove work, set out this season to become more of a threat offensively. He's hitting .287 with five homers and 25 RBIs, lifting his on-base percentage by 50 points and his slugging by 100 points over 2012.
Crawford is running second at shortstop in the All-Star balloting behind the Rockies' Troy Tulowitzki.
Posey, a star at Florida State University, was no secret. The Giants' good fortune was that four teams elected to pass him by, enabling them to select the player they identified as the best in the Draft.
Crawford was another case altogether. A solid player at UCLA, he was the 13th shortstop taken in that Draft and No. 117 overall in the fourth round -- a slight he would use to fuel his drive to prove so many clubs so wrong.
Posey's impact was almost immediate. He was a driving force in the 2010 title run as a rookie, guiding a dominant pitching staff while producing one clutch at-bat after another.
After a violent home-plate collision ended his 2011 season in May, leaving him with a shattered lower left leg, Posey came back in 2012 to claim the NL Most Valuable Player Award. He led the club offensively as the cleanup man and directed the defense.
After breaking in with 66 games in 2011, Crawford arrived in 2012 as a premium shortstop after a rough start. He partnered with veteran Marco Scutaro, a midseason acquisition from Colorado, in the heart of a superb infield.
That 2008 Draft was Barr's first major assignment with the Giants. Employed by the Dodgers as their East Coast scouting supervisor for a decade, the Audubon, N.J., native moved to San Francisco to serve as special assistant in charge of scouting to Giants general manager Brian Sabean.
While working for the Giants' rivals down south, Barr had fallen in love, as scouts will, with a special athlete.
Barr had followed Posey since his high school days in Leesburg, Ga. Barr marveled at the quickness of his bat, his composure and inner confidence, his across-the-board skill set and versatility.
"I'd spent a lot of time with Buster and thought the world of him," Barr said. "I had the opportunity not only to see his ability and talent but to get insight into his makeup and personality. He was the top guy on our board, the guy we really wanted to have.
"When I was with the Dodgers in 2007, going into his junior year at Florida State, I told him that if there was any way, we'd get him. Now it's a year later, I'm just starting out with the Giants, and I had this feeling it was meant to be. I even told Buster before the Draft that this might be the way it's supposed to happen."
Barr's prayers were answered. Tampa Bay chose Tim Beckham. Pittsburgh took Pedro Alvarez. Kansas City went for Eric Hosmer. When Baltimore selected Brian Matusz, the Giants knew they had their man: Gerald Dempsey "Buster" Posey.
The storied franchise that featured Willie Mays and Barry Bonds had another superstar. This one would lead his team to its first two World Series titles since the team's arrival in San Francisco in 1958.
"I was 16 when I met John for the first time, at a showcase event somewhere in Florida," Posey recalled. "John Barr is a great man."
As thrilled as Giants were with their Posey coup, they would have another reason to celebrate three rounds later.
Barr and Giants area scout Mike Kendall, brother of former catcher Jason Kendall, liked the shortstop at UCLA. Crawford, the Bruins' MVP as a freshman and sophomore, fell off offensively as a junior and watched his stock fall in the Cape Cod League.
Twelve shortstops had been taken when the Giants tabbed Crawford. Between Posey and Crawford they'd drafted third baseman Conor Gillaspie -- now with the White Sox after pieces of three seasons with the Giants -- and outfielder Roger Kieschnick.
Six of those 12 shortstops taken ahead of Crawford have made it to the Major Leagues. Only the Nationals' Danny Espinosa and Gordon Beckham of the White Sox have made impacts -- primarily as second basemen.
"I wanted to go higher and was expecting to go higher," said Crawford, a Giants fan growing up in the Bay Area. "So it's satisfying to be here, in the big leagues. If I had gone earlier, somewhere else, I wouldn't have ended up with the Giants. So it happened for a reason. This is where I was supposed to be."
Barr celebrated his fifth anniversary with the Giants during their World Series sweep of the Tigers. A man who knows all too well the feeling of waving goodbye to a loving wife and four kids to go off on another mission, he is generous in acknowledging the tireless efforts of area scouts.
"Mike Kendall deserves credit for doing a really nice job with Brandon," Barr said. "He's a big-bodied shortstop who's really athletic. We were impressed with his agility and body control, and his arm is plus.
"Offensively, his hand-eye coordination and strength are there. He has some power. He's a great kid, very humble. He's got a sense of humor and a quick wit. He's mature and respected."
A first baseman and center fielder at Ryder College, Barr ventured into the private sector when he wasn't offered a contract. Baseball remained his passion, and the Mets gave him the outlet with his first job. He went on to work for the Twins (1988), Orioles (1989-90), Padres (1991-93), Mets again (1994-97) and Dodgers (1998-2007).
The move to San Francisco brought a magical first year with the Draft, and that was just the start. Two World Series championship rings later, Barr keeps searching for those special players who make a scout's heart sing.