Wheater's late header rescued Bolton from the embarrassment of a third-round defeat at League Two Macclesfield, who had been leading 2-1 but were in the end relieved to hold out for a 2-2 draw.
Cahill's likely move to Chelsea should give a chance for Wheater to revive a career that has stalled somewhat since the dizzy heights of 2008 when Fabio Capello had the then Middlesbrough man on the bench for two England matches.
The 24-year-old centre-back has vowed to grab the chance with both hands.
Wheater said: "I want to be playing and if Gaz does go I will miss him as he's a good friend of mine, but it means there is a chance to get in the team and hopefully stay there.
"It has been stop and start for me this season. I was in the team and then got a red card and was out of it so hopefully I can stay in the team now."
Wheater was referring to his first league start of the season when he played against Arsenal in place of the ill Cahill, and was red-carded for holding back Theo Walcott.
The defender admitted his heart was in his mouth in the first half against Macclesfield when he hauled back Matthew Hamshaw and with the 5,757-strong crowd baying for blood referee Jonathan Moss produced a card - but a yellow one this time.
"I worried a little bit," said Wheater. "I thought here we go again but Joe [Riley] was there covering so the yellow card was the right decision.
"It was good to score too - it has nearly been a year since I last scored and that was for Middlesbrough."
Macclesfield boss Gary Simpson was convinced Wheater should have been sent off but said he would not make a song and dance of it.
"He was the last man so if that had us been pulling one of them back would he have gone? Let's leave it at that," Simpson said.
Arnaud Mendy's spectacular volley had given the League Two side hope of an upset before Wheater's header. Ivan Klasnic had earlier put Owen Coyle's side ahead, before Colin Daniel fired Macclesfield level, and the Silkmen had dominated much of the match until they ran out of steam.
Simpson said the draw was a fitting tribute to the memory of midfielder Richard Butcher and former manager Keith Alexander.
The tie marked the first anniversary of the death of 29-year-old Butcher from a heart condition, and Simpson, who had been assistant to Alexander when he died aged 53 in 2010, said it had been an emotional day.
Simpson said: "Butch and the gaffer were a big part of this football club so it was a fitting way the lads went out and performed.
"Nobody would have been more proud of them than the gaffer and Butch.
"It was a good effort by us against the cream of our country - a team from the Premier League."
Simpson admitted the odds were against the Silkmen pulling off an upset at the Reebok Stadium but refused to give up hope.
He said: "I am a bit of a realist and usually the first bite of the cherry is the only one you get but we played quite well up there in the Carling Cup so we will give it another go."
Cahill was not in the squad for the match and it now looks likely he has played his last game for Wanderers.
Asked if that was the case, Bolton boss Coyle said: "I'm not a party to the talks but if they conclude it then he won't, and if they don't then he will - it's very simple.
"We as a club have agreed a fee with Chelsea. I said to Gary and his representative to conclude that with Chelsea - if they do then great and if they don't he's a Bolton Wanderers player."
