Sen. Lindsey Graham said Monday that his friend and colleague Sen. John McCain had been feeling sick for awhile before his surgery Friday to remove a blood clot above his left eye.

"It [was] a routine check, but John had not been feeling good," Graham, R-S.C. told CNN Monday. "He had been traveling a lot, wrote it off to being tired, but he was being forgetful and just wore himself out traveling around the world. I'm glad they found what I think was the cause."

McCain, R-Ariz., had a craniotomy, a procedure in which doctors create an opening in the skull, and is recovering at his home in Arizona.

Graham seemed to suggest that McCain, 80, had symptoms in the weeks before his surgery.

In June, McCain delivered confusing questioning of James B. Comey, the former FBI director, that raised eyebrows. McCain jokingly dismissed the worries by saying he had stayed up too late watching baseball the night before.

His surgery Friday prompted Senate Majority Leader Mitch McConnell, R-Ky., to delay a vote on the Republican healthcare bill until after this week.

Republicans need McCain's vote for the measure to pass, but the senator has not yet revealed his position on the bill.