Las Vegas oddsmakers believe this Super Bowl is one of the most evenly matched ever.

Bettors seemed to favor the Denver Broncos early, though, and sports books on the Las Vegas Strip quickly adjusted their lines to make Denver anywhere from pick 'em to a 2-point favorite to win the title game.

Some sports books made the Seattle Seahawks favorites while others put up lines favoring the Broncos in a rare split for a game that could be the most bet ever. Still others played it down the middle.

Bettors quickly lined up to back their opinions with money. At the South Point hotel's sports book, a bettor put $25,000 on the Broncos within minutes of the end of Sunday's second game, moving the line from pick 'em to the Broncos favored by one.

Officiating upgrade: In an attempt to improve officiating next season, the NFL has spent this past year grooming 21 officials in its newly created developmental program with the idea that these officials will be better prepared to step into games as early as next season, a league source told ESPN. The belief is many of these officials can step in and provide immediate results.

NFL commissioner Roger Goodell has made no secret that he would like to upgrade the league's officiating.

Draft record: A record 98 underclassmen, including Johnny Manziel and Jadeveon Clowney, have made themselves eligible for the draft in May.

The league released the list of early entrants Sunday and said the number has risen six straight seasons. The deadline for underclassmen to apply was Jan. 15.

Last year, 73 underclassmen entered the draft. The year before it was 65, and in 2011 it was 56.

Cal, which went 1-11, has six players listed among the early entrants, but that includes defensive end Chris McCain, who was dismissed from the team in September.

Stanford has three early entrants (all starters): All-American guard David Yankey, tackle Cameron Fleming and all-conference safety Ed Reynolds.

LSU for the second straight season had the most players of any school to leave early. The Tigers had seven early entrants this season, including wide receivers Jarvis Landry and Odell Beckham Jr., after 11 LSU players left early last year.

The draft is May 8-10 in New York.

Thursday night TV: All four of the NFL's network partners have bid on the Thursday night television package, a person with knowledge of the bidding process told The Associated Press.

The league has used its NFL Network to televise the games but recently put up the 13-game series for bids and received them from NBC, Fox, CBS and ESPN. The person spoke on condition of anonymity because the bidders are not being made public.

Turner Sports has also bid, and there's a strong possibility ESPN would put the games on ABC should it be chosen by the league.

Bears: Quarterback Josh McCown, who will be a free agent this offseason, has no intention to retire, a source close to the 34-year-old veteran told ESPN.

In what promises to be a thin crop of free-agent quarterbacks, NFL executives believe McCown and Michael Vick will be the top two options.