"I knew where I wanted to be," Cook said. "I think this team is so close to getting to the Super Bowl, and I want to help in any kind of way."
Coach Andy Reid said the Eagles brought Cook back because he is an experienced safety who knows defensive coordinator Jim Johnson's system. Cook has also been a valuable special-teams player the last four years.
"I kept in contact with the team and let them know I was going through my rehab," Cook said. "I wanted to do everything I could to get back out there, and the Eagles were open to bringing me back."
The Eagles were also skeptical that Cook could recover from the major surgical procedure he had on his right knee in December. The 5-foot-11, 205-pound safety suffered a severe cartilage tear during the third game of the season against Dallas.
Initially, he underwent arthroscopic surgery and tried to make a quick return. When that didn't happen, Cook went on the injured-reserve list in November and had an operation known as microfracture, which is designed to regenerate cartilage in the knee.
"The success ratio of that surgery is very low," Reid said. "We brought him in and did an MRI and it was positive. He was able to go through a workout with us and that was positive. Does he need to get back into game shape? Absolutely. The guy he was working with in rehab did a great job, and as a result he is going to come back here and compete."
Cook worked out with personal trainer Steven Kotter.
"We kind of set up our own little gym on the beach," Cook said. "He was real good. We did a lot of different stuff in the sand and in the water. We were running in the ocean while a lot of other people were sunbathing."
Though the odds were stacked against him, Cook said he never allowed negative thoughts to creep into his head.
"It was a long process," he said. "I had the surgery back in December, but it never crossed my mind that I wouldn't make it back."