The pair's presence was key in a 2-0 win at Turf Moor which also marked a first clean sheet of the campaign.
Neville, who won six Premier League titles with United, believes the safety net provided by Fellaini and Matic will allow Paul Pogba the freedom to focus on being a goal threat at Vicarage Road.
He feels it will also make the centre-backs less exposed than earlier in the season.
"They’ve tried [Ander] Herrera and Fred. But I think with these two there’s real solidity now," says Neville in the video above.
"When you see Pogba in the box looking to score, Matic and Fellaini are providing protection."