(CBS) The Bulls and wing Jimmy Butler still have a gap to bridge in contract extension negotiations before Friday night’s deadline, according to multiple reports.

As of Thursday afternoon, the Bulls and Butler had a “large” gap to overcome, according to the Tribune’s K.C. Johnson, who on Wednesday reported that the sides were around $4 million apart in annual pay. The sides are believed to have gotten closer to an agreeable number but are still several million apart annually, reports indicated, and plenty of doubt remains as to whether a deal will get done.

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An extension for Butler is looking “increasingly unlikely” before the deadline, TNT’s David Aldridge reported on Thursday.

The exact dollar values the sides are proposing for Butler haven’t been reported, but Butler’s representatives likely have in mind the four-year, $63-million deal that Utah’s Gordon Hayward signed last offseason. Hayward’s proved to be a better offensive player than Butler, but the deal shed some light on the market value for wings, and Butler is one of the NBA’s top perimeter defenders.

Butler also had a stellar preseason, leading the Bulls in scoring and playing consistent at both ends of the floor.

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In offering less than what Butler’s camp desire, the Bulls are likely pointing to the fact that Butler shot 40 percent overall and 28 percent from 3-point land last season, numbers that are below what teams desire out of their two-guards.

Adding to the intrigue is that because of a new media rights deal that kicks in for the 2016-’17 season, the NBA’s salary cap is expected to take a large jump that year, with some suggesting it could rise to around $90 million. It’s currently about $63 million. An annual value that might seem like an overpay in 2015-’16 could well look fair in 2016-’17, and players are surely keeping that in mind.

Fourth-year pros like Butler who were first-round picks have until Friday night to be extended before they set on a path to becoming a restricted free agent at season’s end. If Butler becomes a restricted free agent, the Bulls could simply keep him by matching any offer sheet he signs. But in that case, they’d risk paying him more than what they think he’s worth or watch him walk if they don’t match.

Butler has said he wants to remain in Chicago in the long term.

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Two seasons ago, Bulls forward Taj Gibson saw his contract negotiations go right down to the wire, eventually signing an extension just minutes before the deadline and after a game that evening. A similar situation could play out Friday night, when the Bulls host the Cavaliers at the United Center.