Speaking after the game, Vikings coach Kevin O'Connell said the team sent Jefferson for further evaluation to rule out any serious internal injuries after a hit by Raiders safety Marcus Epps. Jefferson returned to Allegiant Field by the end of the game, but whether he'll be ready to play next Saturday at Cincinnati Bengals has not yet been determined.
"It looks like we avoided any significant thing there," O'Connell said.
Jefferson's absence played a notable role in the Vikings' failure to score until Greg Joseph kicked a 36-yard field goal with 1:57 remaining in the game. It was the lowest-scoring indoor game in NFL history and the first to end 3-0 since 2007.
O'Connell said he was not ready to name a starting quarterback moving forward, citing the need to assess other injuries sustained Sunday -- from Jefferson to right tackle Brian O'Neill (ankle) to running back Alexander Mattison (ankle).
Jefferson's injury occurred with 9:54 remaining in the second quarter, when he jumped to catch a high pass from Dobbs and was hit hard by Epps after a 15-yard reception. Jefferson grabbed his lower back and immediately left the field. In all, he caught two passes on three targets for 27 yards while playing a total of 13 snaps.
He was playing in his first game since suffering a right hamstring injury in Week 5, which forced him to miss seven games. He did not start Sunday but jogged onto the field for the second play of the game.
Jefferson opened this season on a blazing pace, averaging an NFL-high 135.8 yards per game during the first four weeks of the season -- a rate that would have obliterated Calvin Johnson's NFL single-season receiving yardage record (1,964) by Week 15. Jefferson had been stuck at 571 yards since suffering the hamstring injury, and the Miami Dolphins' Tyreek Hill (1,481 yards) is the player with the best chance of breaking Johnson's record this season.
Jefferson said last week that his new goal for the season was to finish with 1,000 yards. That might be difficult after his latest injury.
"It's been hard to adjust those goals honestly," Jefferson said last week. "To have missed seven games throughout the season, especially on the pace that I was going before the injury. It's a little tough to see Tyreek going crazy every single week, to see different people throughout the whole league doing tremendous things. It's been tough because it's the first season that I've been hurt since I've been into the league."