Juventus' defensive frailties were again exposed as it labored to a 2-1 win at home to Sporting Lisbon in the Champions League on Wednesday.
Mario Mandzukic scored the winner six minutes from time after free-kick specialist Miralem Pjanic had canceled out an own-goal by Juventus defender Alex Sandro in the first half.
Juventus, which has reached the final twice in the last three seasons, remained three points behind Group D leader Barcelona after the Spanish side beat Olympiakos 3-1. It moved three points above Sporting.
"It's a period in which we're not playing brilliantly, we have had injuries and some players haven't come back in good shape after the international break," Juventus coach Massimiliano Allegri said. "We need to remain focused. What we did last year is in the past."
Allegri's side had dropped points in its previous two Serie A matches and made a series of errors in a 2-1 home loss to Lazio on Saturday.
Juventus has struggled defensively this season following the departures of Leonardo Bonucci and Dani Alves, and Sporting stunned the Allianz Stadium by going in front in the 12th minute.
A Bruno Fernandes pass came through to Gelson Martins, whose effort was parried by Gianluigi Buffon but the ball rebounded off Sandro and into the back of the net.
That appeared to spark Juventus into life and Mandzukic would have leveled but for a perfectly-timed tackle from Jeremy Mathieu.
The hosts did equalize in the 29th when Pjanic marked his return from injury by placing a free kick into the top left corner.
Juventus almost went in front seconds later but Mandzukic fired just past the left-hand post.
Allegri threw on Douglas Costa for Stefano Sturaro in the 84th minute and the substitute made an immediate impact. Just 13 seconds after coming off the bench, he provided the cross for Mandzukic to head home.
"We're in a group with Barcelona and Juventus, clubs which have played well in the Champions League in recent years," Sporting coach Jorge Jesus said.
"We deserved to be drawing 1-1 at the break. In the second half, in our best period, I thought we could even maybe win the match. I have to congratulate my players, we didn't win but there was definitely something positive."