By Jonathan Davies Former rugby union and league great

Everyone knows when the time is right to call it a day - and only Jason Robinson knows whether he's timed it right.

Robinson's main asset was his ability to beat a man one-on-one - and he was a fantastic finisher

He's done everything he wanted to achieve when he crossed over from rugby league.

He's won a Grand Slam, a World Cup, scored a try in the final, played for the Lions - and maybe the commitment now is too much for him.

I don't think he's played to his best over the last season and maybe he's not been playing in his best position at full-back.

But I actually think form is temporary, class is permanent and this season he could be back to what he's capable of doing for Sale.

He had a quiet time last year and maybe he lost the edge because he was playing too much.

When he was drafted into the England team in 2001, he brought professionalism and a strong work ethic.

But his main asset was his ability to beat a man one-on-one - and he was a fantastic finisher.

The England team needed a spark. They dominated teams up front, but sometimes they couldn't capitalise on the possession and pressure.

But when Robinson came along, he changed all that. Without a shadow of a doubt he's been the most successful rugby league convert ever.

You can mention his honours but for me the abiding memory is of his flying feet From A Have your say on Scrum V

He joined Bath with Henry Paul in 1997 and I remember playing against them and they found it very hard to adjust.

But it just shows what a person he is that he worked hard and got his head down to become the great player he is.

He couldn't kick a pin when he was playing rugby league, but he worked on that and became a world great.

Losing a player of Jason's character is another blow for England coach Andy Robinson.

On his day Jason Robinson would be in the England side and even if he wasn't in the starting line-up, he would provide strength in depth.

Robinson's still only 31 and has a lot of rugby left in him.