(Reuters) - The Indianapolis Colts and their fans got an early Christmas gift when head coach Chuck Pagano returned to work on Monday, three months after being forced to the sidelines to battle cancer.

Diagnosed with leukemia in late September, Pagano spent the last three months undergoing treatment, including chemotherapy, while his inspired team led by rookie quarterback Andrew Luck battled on the field earning an unlikely playoff spot.

"Circumstances don't make you, they reveal you," an emotional Pagano told reporters after reporting for work at the teams Indianapolis training facility. "The way I look at it is, my job has just begun.

"Besides my job here...my job now is to give back everything I can possibly give back to everyone out there who's fighting some type of illness, some type of disease, some type of cancer."

The Colts, who tied for the NFL's worst record last season at 2-14, improved to 10-5 with their win over the Kansas City Chiefs on Sunday clinching an AFC wild card.

After three games into a rebuilding season, the Colts learned Pagano would take indefinite leave to fight his cancer and was replaced by assistant coach and offensive coordinator Bruce Arians.

The goal of the Colts became to keep playing until Pagano could return to work.

Indianapolis went 9-3 under Arians, who will hand over the head coaching job back to Pagano for the regular season finale this Sunday against the Houston Texans.

"It's a fairy tale," said Colts owner Jim Irsay. "It's a Hollywood script. But it's real."