Dallas Cowboys left guard Nate Livings is having another surgery on his right knee, ESPNDallas.com reported Friday.
Livings had surgery in February and is slated for a second operation. He had to sit out organized team activities in May after aggravating the knee. He took first-team snaps during training camp before sitting out Thursday's practice with knee soreness.
He is expected to need two to four weeks of recovery time, which may affect his playing status for the regular-season opener against the New York Giants on Sept. 8.
The Cowboys signed linemen James Nelson and Jeff Olson on Thursday. The team is also looking at free agent lineman Brian Waters.
Livings started all 16 games last season for Dallas.