Weeks is out for the season after tearing a tendon in his left wrist in Sunday's 8-2 win over St. Louis. He'll undergo surgery on Wednesday.
Weeks, Milwaukee's regular leadoff batter, was hitting .272 with nine homers and 24 RBIs. His home run total ranked second among NL second basemen behind Philadelphia's Chase Utley.
The 24-year-old Iribarren was hitting .308 with 10 doubles, a homer and 19 RBIs in 35 games with Triple-A Nashville. He also had six stolen bases.
The Brewers opened a three-game series in Houston on Tuesday.