SALT LAKE CITY (AP) - For about 5 seconds, the ball was just lying there in the end zone at the feet of Oregon's Erick Dargan. Utah's Kaelin Clay was celebrating with his teammates what looked like a long touchdown catch to put the Utes up 14-0 in the second quarter against the fifth-ranked Ducks. Joe Walker knew better. Clay had nonchalantly dropped the ball a yard before crossing the goal line. Walker returned Clay's careless goal line fumble 100 yards for a touchdown and Marcus Mariota threw three touchdown passes and ran for another score as Oregon turned back No. 20 Utah 51-27 on Saturday night. The Ducks scored the final 21 points after Utah got within three early in the fourth quarter. "A gutty, gutty win by our team," Oregon coach Mark Helfrich said. A huge turn of events, obviously, on the fumble going into the end zone. A great lesson for all of us. Mariota was not at his best, but he did nothing to hurt his Heisman Trophy hopes while keeping the Ducks (9-1, 6-1 CFP No. 4) in the thick of the College Football Playoff race. The junior ran for 114 yards and was 17 for 29 for 239 yards passing. Oregon also clinched the Pac-12 North and a spot in the conference championship game on Dec. 5, but lost a key player. Tight end Pharaoh Brown was carted off after an ugly right leg injury in the fourth quarter. Utah's Travis Wilson didn't get the start, but threw for 297 yards and two touchdowns after Kendal Thompson went out with a knee injury in the first quarter. Clay had 152 yards on five catches, but it was the 1 yard he let slip away that will be remembered most. The Utes (6-3, 3-3) were on their way to taking a two-touchdown lead on the first play of the second quarter when Wilson connected with Clay on a deep ball down the middle. Clay was cruising but, but he left something important behind. I thought he might have dropped the ball a little early. I wasn't too sure," Walker said. I saw the ref throw the bean bag (to indicate a fumble). Ran down there, picked up the ball. Dargan grabbed it first, got into a scrum with a Utah player and lost it. Walker then grabbed it and took off the other way. By then there was a flock of Ducks leading him against only one Utah player and Walker chugged in to tie the game at 7. The Utes and their fans were stunned silent. Clay slumped down on the bench and briefly pulled his black head band down over his eyes. "I know how important points are, so I take full responsibility," Clay said. I got carried away. The play covered 178 yards - 78 one way and 100 the other. Oregon scored the next 17 points, including two short touchdown passes by Mariota. Utah gave Thompson his second start of the season, hoping his quickness and ability to run the option would come in handy against the Ducks. He led the Utes to a touchdown on their first drive, but on the next Thompson's knee appeared to buckle as he threw a deep pass. The junior went down and needed to be helped off. He left the sideline and returned later in street clothes. Devonate Booker, the Pac-12 second-leading rusher, had a big day as a receiver with eight catches for 110 yards, including a 27-yard touchdown with 3:28 left in the third quarter that cut the lead to 27-20. The Ducks' responded with a field goal and Wilson came back with a 13-yard touchdown pass to Westlee Tonga to make it 30-27 with 11:48 left in the fourth quarter. The Ducks then finished with one of their trademark spurts. Mariota fired a dart down the middle to Dwayne Stanford for a 34-yard touchdown. After a missed field goal by Utah, Mariota raced around the corner for a 1-yard touchdown with 4:51 left to make it 44-27. The Ducks have won five straight since losing to Arizona and seemed to have fixed the offensive line issues that hampered them early in the season. There might be more problems to address. Playing without injured right tackle Matt Pierson, the Utes sacked Mariota on consecutive plays on the opening series. The Ducks also lost star center Hroniss Grasu to an injury in the fourth quarter. "We weren't able to dictate the tempo," Mariota said. They did a good job of getting us in sacks and getting us in long yardage situations. It wasn't favorable for us. Oregon managed to keep Mariota upright by moving him in the pocket and throwing a lot of quick passes. The Utes, who lead the nation in sacks, finished with four. "Definitely not a garden variety 51-27 win," Helfrich said. But a big, big win for a lot of reasons. Follow Ralph D. Russo at www.Twitter.com/ralphDrussoap