The England international limped off at halftime in the Premier league clash after a tackle with Liverpool midfielder Yossi Benayoun, and was sent immediately for an X-ray.
Initial reports from Old Trafford suggested the injury was purely muscular, but a subsequent check-up discovered a break in his right foot.
Carrick is now out of United's Champions League opener against Villarreal, along with their Premier League showdown with Chelsea at the weekend.
The 28-year-old is also set to miss England's World Cup qualifiers against Kazakhstan and Belarus in October
