Roberts shows off-field speed for son

James Roberts is the NRL's fastest man but he feared he would not be quick enough to catch the birth of his first child after their last round win.

James Roberts feared he wouldn't catch the birth of his first child after last week's NRL match. (AAP)

It's early days but it seems Brisbane speedster James Roberts' son may not be a chip off the block.

Much to Roberts' relief.

Roberts' partner Anna went into labour on the Gold Coast hours before last round's NRL home clash with South Sydney was about to start.

He rolled the dice and opted to play last Friday night's match, showing his blistering speed to score a second half try off a Ben Hunt kick and secure a 30-8 win.

But the NRL's fastest man showed more pace after the match as he raced back to Gold Coast hospital.

However, his son was in no hurry.

His partner finally gave birth in the early hours of Sunday morning, ending a marathon labour.

"I thought it was close - the water broke the day before (the game) but it dragged on a bit," Roberts said.

"She was begging me to stay and not go but I just wanted to come up and do a job for the boys."

Roberts admitted it was a tough call to play - one that even master coach Wayne Bennett didn't want to make.

"I am sure Wayne did (want me to play) but he didn't want to say anything," Roberts laughed.

"I think he was just avoiding calls from Anna."

Fatherhood is agreeing with Roberts.

"There is a bit less sleep but it's pretty enjoyable going home to my little boy," he said.

Now life has settled off the field, Roberts looked forward to showing what he could do on it.

The man who infamously claimed he had "more speed than Oxford Street" was ready to find another gear against the Sharks this weekend.

"I am not fully impressed with my form but I am focusing on my defence this year," he said.

"I have got a bit more ball in the past few games but it will come.

"As long as we are winning games I am happy."