Anelka was the focus of much pre-match attention at The Hawthorns after the controversial 'quenelle' goal celebration last weekend which could yet see him face disciplinary action.
The Frenchman did not get on the scoresheet again but was a prominent member of hard-working attack that eventually earned reward for their efforts with a late Saido Berahino penalty.
Substitute Berahino struck from the spot in the 87th minute as the managerless Baggies saw off 10-man Newcastle 1-0 to secure a first Barclays Premier League win in 10 games.
Anelka's selection, after the furore he sparked by performing the quenelle gesture at West Ham, was one of a number of talking points from a slow-burner of a contest played out in persistent rain.
Downing said: "I thought he contributed - not in terms of getting goals like at West Ham - but I thought he was important, particularly after the sending off.
"That creativity and ability to unlock tight defences, when it started to get a bit frantic - it was important he was still on the pitch to do that."