Cadete was restored to the attack after missing Monday's cup tie against Hibernian because of international duty. His inclusion came at the expense of Pierre Van Hooijdonk and Andreas Thom who were both relegated to the sidelines, alongside Celtic's latest acquisition, the Italian defender Enrico Annoni.
Motherwell were never allowed the time to find the kind of rhythm that saw them smash five past Raith on Tuesday with Celtic threatening almost from the kick-off with a second-minute volley from Peter Grant which was blocked on the line.
They should have opened the scoring after six minutes when Simon Donnelly broke down the right but Cadete and Paolo Di Canio both went for the same ball, neither getting a touch.
But Cadete struck after 10 minutes following some slick Celtic inter- play. The referee, Jim McCluskey, let play go on after a foul as Donnelly, Di Canio and McNamara combined, and the striker neatly side-stepped Scott Howie to complete the move.
On the half-hour, after Stephen McMillan had collected a deserved booking for a lunge on Phil O'Donnell, Cadete passed up a great chance to make it two when he was sent clear, but Howie saved well with his feet.
At the other end, Stewart Kerr was required to pull off a similar save from Eddie May but it was a rare opportunity for Alex McLeish's side.
The Celtic manager, Tommy Burns, was pleased with the result despite a rather dismal spectacle: "I'm delighted to get a vital victory. We've not had many at Fir Park over the last few years and the players dug in well."Reuse content