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.
It was a victory the hosts deserved for their greater enterprise, particularly after the sending off of Mathieu Debuchy for a two-footed tackle on Claudio Yacob on 62 minutes.
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."
Anelka himself spurned a glorious chance when he shot over late in the first half and Liam Ridgewell also sidefooted wide from close range late on.
But West Brom finally broke through after Matej Vydra was tripped by goalkeeper Tim Krul, who was perhaps fortunate himself not to be sent off.
"I thought it was a penalty," said Newcastle boss Alan Pardew. "Fortunately the forward had a big touch, otherwise we might have lost another player."
Pardew also did not contest the straight red card for Debuchy, which leaves him facing a suspension.
He said: "I don't think we can have too many complaints.
"There was no malicious intent but you can't take off with two feet like that."
It was Newcastle's second successive defeat after losing just one of their previous nine matches.
Pardew felt the Christmas schedule might have taken its toll.
He said: "I thought both teams look heavy-legged."
For West Brom, the Anelka distraction aside, the atmosphere does seem to have lifted under Downing after the gloom and poor form that led to Steve Clarke being sacked last month.
The team are now unbeaten in four games under the temporary boss, who again denied he wants the job permanently.
He said: "I was always in a support role and that is what I intend to do.
"The uncertainty can't go on. There has to be a decision eventually.
"They can't just keep making me caretaker in the next month."