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Clemson upset Alabama 35-31 in the last second of the college football championshipby Mike Denison

The Clemson University Tigers upset the Alabama University Crimson Tide 35-31 Monday night in an instant classic College Football National Championship game.

Clemson quarterback Deshaun Watson threw the game-winning touchdown with one second remaining to complete the upset. 

Alabama was the top-ranked team all season and was undefeated heading into Monday night. Coach Nick Saban had never lost a championship game before. In 2016, Alabama beat Clemson 45-40 for the title.

Here's the game-winning pass to Hunter Renfrow.

All Alabama fans can do is speculate now. Coach Nick Saban fired offensive coordinator Lane Kiffin last week and brought in Steve Sarkisian to replace him. Star running back Bo Scarbrough was injured in the third quarter and had to leave the game. 

Scarbrough's dominant first half gave Alabama an early lead.

WATCH | Clemson players were, as you can imagine, extremely excited after the game. 

Watson's win didn't come easy. He took a lot of hits from Alabama's fierce defense.

Sports Twitter continued to be weird, glorifying ref Mike Defee's arms.