The Home Run Derby will be broadcast live tonight on ESPN and MLB.com at 8 p.m. ET. A special one-hour pre-Derby show will be streamed on MLB.com beginning at 7 p.m. ET.
Howard, who won the Home Run Derby last year at PNC Park in Pittsburgh, returns to defend his title against an All-Star lineup that figures to put up quite a challenge.
"It was fun last year and an honor to be invited back, whether I'm on the [All-Star] team or not," said Howard, who hit 23 homers in the 2006 event.
"He's the reigning champ," Phillies manager Charlie Manuel said. "If you watch him take batting practice, I'd say he stands a good chance of winning the thing."
Fielder leads the National League with 29 homers, and is one off the Major League lead, behind Alex Rodriguez of the New York Yankees. The Brewers first baseman, who will be competing in his first Derby, is part of a field that includes four of the top 10 and six of the top 20 home run hitters in the Major Leagues this season.
Both reigning MVPs -- Morneau for the AL and Howard for the NL -- are in, along with two sluggers listed among the top 25 in Derby homers (Howard and Pujols).
Morneau has hit 24 home runs this season, ranking him second in the American League, behind Rodriguez. Last season, Morneau became the first Twins player since 1987 to hit 30 or more home runs in a season, belting 34.
Pujols, tied for 17th in the Major Leagues this season with 16 homers, has hit 34 or more home runs in each of the last six seasons and has averaged 44 per season each of the last three years, including a career-best 49 in 2006.
The six-time All-Star has competed in the Home Run Derby once previously, finishing second to Garret Anderson of the Angels in the 2003 Derby at U.S. Cellular Field in Chicago. Pujols hit 26 home runs in that event, a total that has been topped only twice under the current format, by Baltimore's Miguel Tejada (27 in 2004 at Houston) and then-Phillie Bobby Abreu (41 in 2005 at Detroit).
Rios, who was an All-Star last year but did not play or compete in the Derby, has 17 homers and is batting .294 with 53 RBIs.
"I'd love to see that, especially a right-handed hitter in San Francisco," Toronto manager John Gibbons said recently when asked about Rios competing in the Derby. "For my money, he'd have a good chance to win that thing."
Guerrero, who competed in the 2000 Home Run Derby at Atlanta's Turner Field as a member of the Montreal Expos, is batting .325 with 75 RBIs. The Angels outfielder is tied for 37th in the Major Leagues with 14 home runs.
Ordonez, the first Tiger to compete in the Derby since Ivan Rodriguez did so at Comerica Park two years ago, leads the Major Leagues in batting. He hit 24 homers last season for the AL champions.
Derby contestants get 10 outs in the first round to hit as many home runs as possible. An out is recorded when a player swings and does not hit a home run. The four players with the most homers in the opening round advance to the semifinals, and the two with the most home runs in the semifinals advance to the championship round.
Totals from the first round carry over to the second round, but homers from the first two rounds do not carry over to the championship round. The player who hits the most home runs in the championship round will be declared the State Farm Home Run Derby champion.
The 78th Major League Baseball All-Star Game will be televised nationally by FOX Sports, in Canada by Rogers Sportsnet and Sportsnet HD, and around the world by Major League Baseball International, with pregame ceremonies beginning at 8 p.m. ET. ESPN Radio will provide exclusive national radio coverage, and MLB.com will provide extensive online coverage. XM is providing satellite radio play-by-play coverage of the XM All-Star Futures Game.