The San Francisco 49ers aren’t saying if Jarryd Hayne will be their punt returner this weekend after his dropped catch, but his quarterback Colin Kaepernick is full of praise for the Australian.

Kaepernick, on a six-year $US114 million ($A158.96 million) contract with the 49ers, said he is amazed at how Hayne has picked up the intricacies of the NFL in such a short time.

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“If I went over and tried to play rugby, I’d probably be lost,” Kaepernick told reporters.

“Him coming over and being able to pick up football and the schemes and what we’ve asked him to do in such a short period of time, it’s really been amazing.”

After a headline-grabbing pre-season of impressive plays, Hayne created news for the wrong reason when he fumbled his first punt in Monday’s regular season opener against the Minnesota Vikings.

The 49ers’ special teams co-ordinator Thomas McGaughey wouldn’t say if Hayne or wide receiver Bruce Ellington would return punts, but the Australian will likely be called on again to assist top running back Carlos Hyde with back-up Reggie Bush suffering a leg injury.

If Hayne does regain the punt return job for Sunday’s game against the Pittsburgh Steelers, he’ll be catching high balls from Melbourne punter Jordan Berry.

Hayne is 27 years old, veteran status for most NFL players, but McGaughey put the fumble down to a rookie mistake.

“Young players make mistakes sometimes, trying too hard or trying to do what got them here,” McGaughey said.

“Sometimes they get overzealous.”

One criticism on Hayne from the coaches is he wants to catch and return every ball instead of calling for a fair catch or letting the ball bounce.

“If put in that situation again it’s something I’ve definitely learned from and if I can’t get a clean catch, then I won’t catch it,” Hayne said.