Hayne says complexity of Kelly's playbook factored into NFL retirement

Rugby star Jarryd Hayne says his much-anticipated NFL stint with the San Francisco 49ers was cut short largely due to his new coach's playbook.

Hayne joined the 49ers last year with no football experience, after starring as a rugby league player in Australia and Fiji.

Featuring as a running back and punt returner in the NFL, he initially made waves through league circles, but abruptly retired in May.

Hayne revealed Friday that the complexity of new 49ers head coach Chip Kelly's playbook played a major factor in his decision to retire and return to rugby league.

"I just think with Chip's playbook, it's such an intense playbook that it would just take too much time," he said, according to The Sydney Morning Herald.

Hayne recorded 52 rushing yards on 17 attempts in eight games with the 49ers.

The 28-year-old wanted to play both rugby and professional football, but struggled to acclimate to the NFL.

"I would have loved to have played both. I would love to have played three sports or four sports. I would love to play league, union, sevens, NFL - I would have loved to play all four, but you just can't do it.

"It was hard at the 49ers. With the new coaching staff and the guys that really put the study and that in - it all changed. It was tough, but I worked hard and made the 90-man squad. That meant I'll be back in preseason, but time isn't on my side. I had to make a decision, and being in Fiji was it."