The sportsman confirmed his romance with stunning reality TV star Kate Wright in July after weeks of swirling rumours that the celebrities had become an item.
The mother of his three children died in 2015 aged 34, after her breast cancer returned, and Rio has now opened up in his new autobiography about his feelings about moving on from his wife.
He said Rebecca’s friend Lisa told him she wanted him to share his life with someone again.
‘Rebecca told Lisa something in the final weeks of her life,’ Rio writes in his new book Thinking Out Loud, which is serialised in The Sun.
‘Months later Lisa told me what it was… ‘It kills me to think of Rio with a new partner, Lisa, you know it does. Of course it does.
‘ “But you know what kills me even more? Thinking of him alone and lonely. If I don’t make it, Lisa, I don’t want Rio to be miserable. I want him to be happy.” ‘
‘To my total surprise, I met someone and at first I wasn’t sure I should let free my feelings,’ he adds.
‘In an emotionally vulnerable state, one’s judgement can be all over the place.
‘I wanted to get to know this beautiful young woman better and, as I have done on occasions, turned to Lisa for advice.
‘Of all the things Lisa has done for me, this may have been the hardest. Rebecca had been her best friend.
‘It’s a measure of Lisa’s love that she put aside her feelings, offered friendship to this stranger and gave the relationship her whole-hearted encouragement. I will be forever in her debt.’
Rio admitted he treasures the happy moments with his children Lorenz, Tia and Tate, more than he did before Rebecca passed away, and said her death taught him to be more ‘loving’.
‘I’ve had to be taught this stuff — but I’m learning. Slowly but surely, I’m learning.
‘The heartbreaking truth is that losing Rebecca has made me more loving. I can’t turn back the clock and show her more love, but I can try not to repeat the same mistakes with our children.’
He added: ‘Being able to cry makes me feel more alive, and for that I am profoundly grateful.’
But he’s reportedly keen to turn things around in his personal life too, as friends close to the star have revealed he is preparing to ask Kate to marry him.