The running back’s contract includes just under $21 million in guaranteed money, said the person, who spoke on condition of anonymity because the Bills have not announced the deal.

Spiller was to arrive at training camp later in the day. Through Friday morning, he’d missed 11 practices since camp opened July 29.

General manager Buddy Nix declined comment as he left the field following morning practice. A Bills official, walking with Nix and CEO Russ Brandon, said the team would make an announcement once the contract had been signed. ESPN first reported the deal.

Spiller, selected ninth overall out of Clemson, took part in all of the team’s offseason minicamps in May and June. But he has some catching up to do, with Buffalo installing a new offense under first-year head coach Chan Gailey. Spiller is expected to play a significant role in the scheme — as rusher and receiver — while sharing time with running backs Fred Jackson and Marshawn Lynch, who split the starting duties last season.

The ACC’s player of the year last season finished his four-year college career with 51 touchdowns, including 32 rushing. Listed at 5-foot-11 and 196 pounds, Spiller has dynamic speed and is unafraid to run up the middle.

Because of his versatility, Spiller has drawn comparisons to Reggie Bush of the New Orleans Saints. Spiller and Bush are the only two players to finish their college careers with 3,000 yards rushing, 1,500 yards in kickoff returns, 1,000 yards receiving and 500 yards in punt returns.

The deal comes a day after Spiller celebrated his 23rd birthday and after the player hinted on his Twitter account Thursday that a contract might be in the works. Referring to his birthday, he wrote: “I gt feelin it’s going be special.”

After practice Friday, Jackson said he’s remained in contact with Spiller through contract talks, and expects the player to be up to speed for practice.

“He’s been in his playbook and all the notes he took, so I expect him to come right in and get in the mix of things,” Jackson said.

Jackson had a career-best and team-leading 1,062 yards rushing last season, and has no trouble giving up some playing time or with the team’s decision to draft Spiller.

“It’s a business. They do what they’ve got to do and I’ve got to do what I’ve got to do,” Jackson said. “The reps I do get, I’m going to take care of them and continue to try and make plays when I get out there.”

The Bills have two other running backs on their roster, Joique Bell and Chad Simpson, both rookie undrafted free agents

Nix, Gailey and Bills owner Ralph Wilson all praised Spiller in the days after he was drafted.

Wilson referred to Spiller as “one of the best players in the country,” and someone who could provide a spark to what he called a “dull team.” Buffalo’s offense has ranked 25th or worst in yards gained the past seven seasons.