Hager was released by the Diamondbacks on Thursday.
Hager was reassigned to minor-league camp by the Diamondbacks on Sunday.
The Diamondbacks announced Saturday that Hager was re-signed on a minor-league deal that includes an invitation to MLB spring training.
Hager had his contract selected by the Diamondbacks on Sunday.
Hager was designated for assignment by the Diamondbacks on Monday.
Hager was optioned to Triple-A Reno on Thursday.
Hager started at shortstop for a resting Geraldo Perdomo and went 1-for-4 with a walk in Wednesday's 7-0 win over the Reds.
Hager is out of the lineup for Thursday's game against the Cubs.
Hager started at second base and went 1-for-2 with a walk in Wednesday's 5-3 loss to the Dodgers.
The Diamondbacks selected Hager's contract from Triple-A Reno ahead of Tuesday's doubleheader with the Dodgers in Los Angeles. He'll start at second base in Game 1, batting ninth.