Diesel, the Huskies’ former mascot, died Sunday — one day after his last game Saturday night.

The husky, who retired in 2013, was 12 years old when he died. Diesel was diagnosed with lymphoma on Aug. 21 and was undergoing chemotherapy until his passing Sunday.

Diesel became NIU’s mascot after his owners, Tom Bonnevier and daughter Cassie Cleary, adopted him from the Free Spirit Siberian Rescue in Harvard.

Cleary, a former Huskies cheerleader, said the rescue brought huskies that were up for adoption to the games her freshman year, but the program didn’t return the next year. When her family decided to get a husky from the rescue, she brought Diesel to the stadium to run during home games.

“What’s ironic is … his very first game was against Toledo at Toledo, and we won 35-17 in 2005,” Bonnevier said. “His last road game was 2013 at Toledo, and we won 35-17.”

Diesel always knew when it was time for a football game, and though he was a little more tired than usual on Saturday, he still had the same gameday spirit, Bonnevier said.

“Once I got his — I call it his gameday bag — out, he knew something was going on because he knows it’s football season,” Bonnevier said. “And when I got his bucket of water ready, he was ready to go in the car.”

Bonnevier said Diesel was lethargic all day Sunday, and eventually wouldn’t get up towards the end of the day. He took Diesel to the Buffalo Grove emergency animal hospital that night, where they realized “it was time.”

Diesel’s owners requested a private cremation and will get a Plaster of Paris pawprint along with his ashes, Bonnevier said.

“We’ll see what happens after that,” he said.

Cleary said she will keep Diesel’s Facebook page open so people can say their last goodbyes and post kind words about the football-loving husky.

“He loved doing the football games,” Bonnevier said. “He loved the NIU community and all the fans. Saturday was a special day for him because he toughed it out. … He enjoyed Saturday. If you see any of the Facebook posts of people with him on Saturday, he looked good. So that’s what he wanted — he wanted one last day at Huskie Stadium.”