That might change if talks aren't resolved soon.
"All I can tell you at this point is that we're all still working on it," Nix told a group of reporters after practice Tuesday. "And probably in a couple of days, if he don't [sign], I will have something to say."
Asked if it was too early to make a public announcement about negotiations, Nix said: "Well, it's not too early. It might be late even."
Drafted ninth overall out of Clemson, Spiller is one of three first-round picks who have yet to sign with their respective NFL teams. He's missed eight practices since the Bills opened training camp Thursday, which marks a considerable setback to the new offense first-year head coach Chan Gailey is installing.
Spiller's agent, Gary Wichard, has not returned messages left by The Associated Press.
Gailey and Nix have both spoken highly of Spiller's dynamic play-making ability as a running back and receiver. And Spiller, the ACC's player of the year last season, was already being counted upon to make a significant impact this season after finishing his four-year college career with 51 touchdowns, including 32 rushing.
"It hurts. He did a great job in minicamps. But being here now is a different game," Gailey said. "And it doesn't help anybody. It doesn't help him. It doesn't help us. We hope it gets resolved as soon as we possibly can."
Spiller would be part of a three-back rotation rounded out by Fred Jackson and Marshawn Lynch, who split the starting duties last season. Gailey has previously indicated that he's open to going with a two-back formation at times to get Spiller involved as much as possible.
Even Bills owner Ralph Wilson, a day after Spiller was drafted, praised the former Clemson standout. Wilson said Spiller was "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 in each of the past seven seasons.
Because of his versatility, Spiller has drawn comparisons to New Orleans Saints running back Reggie Bush. 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.
One potential drawback to talks is the wide gap in money going to the two players drafted immediately before and after Spiller was chosen.
Linebacker Rolando McClain, selected eighth by Oakland, reportedly signed a five-year, $40 million contract that will guarantee him about $23 million. Defensive tackle Tyson Alualu, drafted 10th by Jacksonville, signed a $28 million contact with $17.5 million guaranteed.
That leaves Spiller in the middle, as rookie NFL contracts are traditionally slotted in descending order of where the player was drafted.
"I don't want to get into that," Nix said, when asked about the gap. "He just hasn't signed."
Nix is in his first year as general manager, taking over in December after Russ Brandon was promoted to chief operating officer.
The Bills have had an inconsistent history in getting their first-round picks signed early in recent years.
Last year, linebacker Aaron Maybin, selected 11th overall out of Penn State, missed 24 practices and three of the Bills five preseason games by signing nearly a month after training camp opened. Then there was safety Donte Whitner, selected eighth overall in 2006, who missed eight days of camp.
On the other hand, cornerback Leodis McKelvin (11th overall, 2008) missed only two days, while Lynch (12th overall, 2007), missed only one day.