Travis Hafner underwent a brief arthroscopic knee surgery on Thursday morning at the Cleveland Clinic. The Indians' designated hitter needed a quick scope to repair damaged meniscus in the right knee. MLB.com's Jordan Bastian reports that the surgery lasted all of 30 minutes, via @MLBastian:

Travis Hafner's medial meniscectomy for his right knee took all of 30 minutes today at Cleveland Clinic. Return timetable remains 4-6 weeks.

— Jordan Bastian (@MLBastian) May 31, 2012

With the Indians struggling, it's a big blow to lose Hafner for at least a month, especially with Carlos Santana's bat absent from the middle of the lineup for a week as he recovers from a concussion. Hafner was listed as day-to-day as recently as Tuesday, when he took batting practice and did some running in the outfield, but the knee remained inflamed and Pronk was forced to go under the knife.

For more on Hafner's injury, check out Let's Go Tribe.