Eckstein brings to Phoenix an impressive postseason resume that includes a World Series MVP award in 2006 with the Cardinals as well as another World Series in 2002 as a member of the Angels.
Listed at 5-foot-7, Eckstein has been known for his all-out hustle and small-ball approach throughout his eight-year career.
"You admire and respect him, but he can get under your skin a little bit, and I'm glad he's on my side doing that to the other teams," D-backs manager Bob Melvin said.
"He seems to be able to step up at big times and isn't afraid to play on big stages and in big games. You talk about gamers and so forth and his name comes up quite frequently when you talk about the guys that are getting dirty out there. He seems to take his game to a higher level in bigger games. He does some intrinsic things that don't necessarily show up in the box score. It will be a nice weapon for us."
Eckstein has spent the majority of his career at shortstop but was drafted as a second baseman out of the University of Florida and also has played five games at the position this season, as well as 14 in 2001.
That likely will mean less playing time for Augie Ojeda and Chris Burke, who had been filling in at second since Hudson's injury. It also ends all speculation that third baseman Mark Reynolds would be shifted to second.
Eckstein, who signed a one-year contract worth $4.5 million in the offseason, hasn't seen much playing time in 2008. He missed 19 games with a right hip flexor injury in May and after the Jays dismissed John Gibbons, Eckstein has seldom been used by new manager Cito Gaston, as he has gone with younger players Marco Scutaro and John McDonald.
D-backs starting pitcher Dan Haren praised the team's decision to bring in a veteran with postseason experience. It is the team's second acquisition to fill the void of a player who was forced to sit the rest of the season due to injury. The D-backs traded for Adam Dunn on Aug. 11 to man an outfield position after Eric Byrnes injured his hamstring.
"It's not something that all organizations do," Haren said. "Most organizations don't. When I was in Oakland, I loved it there, but if a guy went down, we weren't going to go out and get anybody to fill any holes. We'd go back and get somebody from Triple-A.
"It's nice to see that the guys up above like the GM and president feel like we have a ballclub that can make it to the postseason and build to get there and to be good when we get there."
To make room for Eckstein on the 40-man roster, pitcher Emiliano Fruto was designated for assignment.
Eckstein batted .277 (72-for-260) in 76 games this season for the Blue Jays with 27 runs scored, a home run and 23 RBIs. After Sunday's game at Yankee Stadium, he was batting .357 (15-for-42) over his last 12 games.
Eckstein has a career batting average of .285 (1,151-for-4,032) in 1,041 games for the Angels, Cardinals and Blue Jays. He has scored 583 runs, hit 179 doubles, 18 triples, 31 home runs and collected 307 RBIs and 112 stolen bases over parts of eight Major League seasons.
If the D-backs opt not to re-sign Eckstein in the offseason, they would garner at least one compensation Draft pick.
Beck, 23, was originally drafted by the Blue Jays in 2004, but didn't sign, and was later selected by the D-backs in the 14th round of the First-Year Player Draft.
Beck started the season in South Bend, going 2-0 with a 2.04 ERA (four earned runs in 17 2/3 innings) over seven games, holding opponents to a .186 average (13-for-70) with three walks and 19 strikeouts. Promoted to Class A Visalia on May 2, appearing in his first 10 games as a reliever, Beck went 1-0 with a save and a 1.37 ERA (four earned runs in 16 1/3 innings). As a starter for the Oaks, he went 4-5 with a 4.46 ERA (39 earned runs in 78 2/3 innings) with 14 walks and 65 strikeouts over 13 games.