Kieran Tierney "very important" to Celtic - Brendan Rodgers
Celtic manager Brendan Rodgers said it was as if left-back Kieran Tierney had "never been away" after playing in 3-0 Scottish Cup win over Albion Rovers.
Tierney, 19, made his first start since late October following ankle ligament damage sustained in training.
"There were a number of items I was really pleased with, one Kieran coming back," Rodgers told BBC Scotland.
"His thrust, his combinations with Scotty [Sinclair] up that side is very important for us."
While Tierney lasted an hour against the League One side, Dedryk Boyata was also a surprise starter, and Rodgers insists the central defender has a future at Celtic Park.
"I was also really pleased with Dedryk Boyata, he's hardly played at all but has been doing really well in training," he said. "He was flawless. Sharp in the tackle, defended well, good speed, and passed the ball simple.
"All the players we have, I want to be here. If some want to be playing more they need to look at it themselves. I'm happy with the squad. Because of the form of the other players, Boyata hasn't played but you saw his professionalism."
Sinclair's stunning opener and further goals from Moussa Dembele and Stuart Armstrong helped Celtic ease into the fifth round.
They now face Inverness Caledonian Thistle at home in the next round, the only side to have stopped Celtic taking maximum points in the Premiership this season.
"We have that quality in the team to create goals out of nothing, it was a wonderful finish by Scotty," said Rodgers.
"In the second half we upped the tempo a bit more and we should have more goals, but the clean sheet was important for us."
Sinclair insists Celtic are not thinking about a possible treble, but warned the winter break has refuelled the champions for the remainder of the campaign.
"Having that break has freshened us up," said Sinclair. "We feel much more sharper and we're ready to go again.
"We've just got to take every game as it comes. Obviously we want to win as many trophies as we can. But we've got to make sure the games that count, we win them."