Rebecca, 34, passed away at the beginning of the month, just five weeks after being diagnosed with breast cancer.
Now friends are said to be worried about how footballer Rio, 36, and their children Lorenz, nine, Tate, six, and four-year-old Tia will cope with their loss.
A source told The Sunday People: "Her life expectancy was two to five years.
"I don't know how Rio's going to come back from this. Rebecca kept him grounded.
"He is devastated. It was so sudden. He's set to retire this season, then he will have to look at rebuilding his life.
"Nothing has really sunk in. I think the devastation will hit them in waves."
Rebecca's funeral was held in Sidcup on Wednesday, attended by some of football's biggest stars.
The insider added: "Rio is very popular and everyone loved Rebecca. Alex Ferguson, Robin Van Persie, Wayne and Coleen Rooney were there, as was Frank Lampard's girlfriend Christine Bleakley."