The thought of following Wayne Bennett to the Dragons couldn't do it.

But watching his beloved Broncos struggle proved too much for Tonie Carroll.

Just months after knocking back Bennett's suggestion to play at the Dragons in 2009, Carroll, 33, announced he would come out of retirement to help his battling NRL team for the rest of the season.

After Carroll convinced Broncos coach Ivan Henjak he was ready for a comeback on Monday, Brisbane organised to register the former international barely 24 hours before the deadline.

Broncos boss Bruno Cullen expected Carroll to make his return against South Sydney at Suncorp Stadium in round 19 after next weekend's bye.

It's a timely boost for the injury-hit Broncos who have lost four straight games to fall out of the top eight.

The latest additions to the injury list - Karmichael Hunt (ankle) and Nick Kenny (knee) - underwent scans on Monday but won't know the full extent of their injuries until Tuesday.

There are fears that prop Kenny has seriously injured his knee.

Carroll's manager Daryl Mather confirmed that his charge had spoken with Bennett late last year about following the great Broncos coach to St George Illawarra for one more season.

"St George never made an offer but Wayne had asked him. It was a conversation between Wayne and Tonie who are very close," Mather told AAP.

"But Tonie didn't want to play against the Broncos - that was the bottom line."

Carroll said he would "never" return to the NRL after moving into real estate work on the Gold Coast following Brisbane's heartbreaking 2008 finals loss to Melbourne at Suncorp Stadium.

However, Carroll put up his hand after the Broncos once again struggled through the Origin period.

"We have a bye after Friday night (against the Warriors). You would have to think he would be right for the next game," Cullen said of Carroll's proposed comeback.

"It (the deal) won't be breaking the bank - but I don't think it was a money thing for Tonie.

"He had been watching us play. We have got players out hurt, and we are a bit shy in the forwards.

"He's put his hand up to help the club which is great."

Cullen said Carroll made initial enquiries about a return around a month ago but had to work on his fitness.

Carroll had tried to throw cold water on weekend speculation, saying he was "happy being a fat real estate agent".

But Henjak was satisfied with his conditioning work, prompting the club to organise registration just before the NRL deadline.

Cullen said Carroll had plenty to offer off the bench.

"But at the moment we are not looking beyond him being a bench player and helping guys out who need a spell," he said.

Carroll played 216 first grade games for the Broncos, scoring 58 tries.

He also played 18 Origins for Queensland and seven Tests for Australia as well as representing New Zealand in the 2000 World Cup.

Carroll is the second Bronco to make a comeback this season - Michael De Vere lasted just one NRL game before pulling the pin again.

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