Turin - Gonzalo Higuain got Juventus's Champions League campaign off the mark coming on as a substitute to lift last year's finalists to a 2-0 Group D win over Olympiakos on Wednesday.
Massimiliano Allegri's side needed to reignite their European campaign after falling 3-0 to Barcelona in Spain two weeks ago.
And Higuain hit back after being dropped by Allegri by opening the scoring after 69 minutes and having a hand in Mario Mandzukic's second on 80 minutes at the Allianz Arena.
Juventus are now third in Group D which is led by unbeaten Barcelona but behind Sporting Lisbon - who lost 1-0 at home to the Spanish side - on goal difference.
For Olympiakos a second defeat after their opener to Sporting leaves them rock bottom.
"I made a choice and Higuain wasn't as good as the others," said Allegri of his decision to leave the Argentine on the bench for a second straight game after last weekend's Turin derby.
"But we saw this evening that he already moved differently. He has never been a problem and never will be. He's a player who can make the difference and win us games.
"This evening we played an intelligent game with patience. They had a good match defensively, they blocked the spaces. It wasn't easy but the strongest team won."
Olympiakos coach Takis Lemonis was parachuted in two days ago for his fourth spell after Albanian Besnik Hasi was sacked after a derby collapse to AEK.
But despite the turmoil within their squad Olympiakos proved more than a match early for the hosts in Turin.
Bosnian midfielder Miralem Pjanic pulled out in the warm-up for Juventus with Higuain dropped, moving Mandzukic to the centre-forward role, before the Argentine came on for the last 30 minutes.
Olympiakos pinned back the six-time successive Serie A champions initially before the game sprung to life for the hosts late in the first-half.
Silvio Proto did well in goal in place of Greek international Stefanos Kapino, banished after the AEK defeat.
And the Belgian kept the visitors net unbreached faced with a dangerous Juventus onslaught in the last 15 minutes of the first half.
Juventus star Paulo Dybala failed to add to his tally of 12 goals this season, sending a couple of free-kicks into the wall.
The hosts missed two quickfire chances on 34 minutes when Juan Cuadrado crossed to Mandzukic but his header was flicked over by Proto, who then dived to keep out Stefano Sturaro's header off the ensuing corner.
Olympiakos were very dangerous on the counter but Gianluigi Buffon had his first save on 41 minutes from a Felipe Pardo angled shot.
Juventus had a double chance to break the deadlock just before half-time when Proto again dived to stop Dybala, and Olympiakos narrowly avoided an own goal when Alex Sandro's cross from the left was accidentally deflected off the post by Bjorn Engels.
Higuain proved decisive when he came on after an hour in northern Italy.
Sandro crossed to to the Argentine whose first effort was blocked, but his second beat Proto for his third goal of the season.
Higuain also had a hand in the second goal when the Argentine played in Dybala before the Olympiakos defence knocked the ball into Mandzukic's path.
Juventus defender Andrea Barzagli conceded Higuain had won the game for them.
"Higuain made a difference when he came on. At 1-0 it was easier. We hadn't been concerned he hadn't been scoring, we were calm. We knew well that he was going to become decisive again."