The deal is pending a physical, a baseball official with knowledge of the agreement said today. The official spoke on the condition of anonymity because the contract had not been finalized.

Casey, whose contract is not guaranteed, hit .296 with four homers, 30 doubles and 54 RBIs in 143 games for the Detroit Tigers last season. In 11 seasons, eight with Cincinnati, the left-handed hitter batted .301 with 130 homers and 718 RBIs.

Detroit decided to shift shortstop Carlos Guillen to first base for the 2008 season and told Casey he would not be back. The Tigers later acquired shortstop Edgar Renteria from Atlanta.

Youkilis played 135 games at first base last season. His primary backup, Eric Hinske, appeared in 43 games but is not signed for next season. With Casey, 33, the Red Sox have a better option to shift Youkilis to third base when Mike Lowell needs a rest. Lowell, the MVP of the 2007 World Series, played in 154 games last year.

In 1999, his third season, Casey finished fourth in the NL in batting with a .332 average. He's been chosen for three All-Star games, the last in 2004. He batted .312 in 2005, his last season with the Reds.