The England striker, who was released by the Hammers at the start of the summer, has returned to Upton Park on a three-month deal.
After proving his form and fitness in training, Sam Allardyce has offered the burly frontman another shot at Premier League life.
He must show that he is deserving of an extended stay, with West Ham's need to find cover for the injured Andy Carroll forcing their hand.
Downing, though, is confident that Cole will be a useful asset, with the 30-year-old a proven performer who has the all-round game to trouble top-flight defences.
After playing alongside Cole in a recent behind-closed-doors practice match, Downing told Sky Sports: "He certainly looked good to me.
"I've played with Carlton for years at England, he's a strong boy. He certainly looked like he has been working hard, and I've seen that at the training ground.
"I think he just needs games, games like that to get him fit.
"I think we needed another option. Carlton can bring that.
"He can also play on the floor, as well as being good in the air, so it's a different option for the manager. We need competition."
West Ham take on Manchester City live on Saturday Night Football - Sky Sports 1HD at 5pm