Real Madrid coach Carlo Ancelotti can push his former club Juventus and disciple Antonio Conte closer to the Champions League exit door if they win in Turin on Tuesday.
The two teams, who have won the competition 11 times between them, were both expected to comfortably progress from Group B and Tuesday's match was seen initially seen as little more than some early sparring for the knockout rounds.
But, after drawing with Galatasaray and Copenhagen and then losing in 2-1 Madrid two weeks ago, Juventus suddenly find themselves fighting for survival.
Ancelotti is unlikely to admit it but he may gain some grim satisfaction if he can help eliminate his former club.
He had two difficult years at Juventus early in his coaching career, where despite twice leading them to second place in Series A he was sacked on the last day of the 2000-01 season.
Conte, who has led Juventus to two successive Serie A titles, was his swashbuckling captain at the time and has since gone on to become of Europe's top coaches although he has sometimes shown exasperation at his club's lack of financial clout.
A win for Real, whose only previous away win against Juventus was 51 years ago, would send them into the last sixteen with two matches to spare and leave third-placed Juve with only two points from four games.
Should Galatasaray win away to FC Copenhagen in Tuesday's other Group B game, Juventus would find themselves five points behind the Turkish champions with a trip to Istanbul still to come.
Juventus have failed to win their last five Champions League ties, a run which started when they lost both legs of their quarter-final to Bayern Munich last season.
Worryingly, three of those matches have been at home at the Juventus stadium, which the club had hoped to turn into an impenetrable fortress when it was opened two years ago.
On the other hand, they have won their last three Serie A matches without conceding a goal and will be hoping that Real's defence will be caught off guard, having leaked five goals in its last two La Liga outings.
"Real have plenty of strong players up front who sometimes help out less in defensive areas, which puts their backline under pressure," Juventus midfielder Claudio Marchisio said on Sunday.
"We managed to defend well in Spain, enjoy possession and cause them problems."
Juventus will be without defender Giorgio Chiellini, who was sent off at the Bernabeu a fortnight ago, leaving Marchisio as the only survivor from the team which beat Real on their last visit to Turin five years ago.
"Even when down to ten we played an excellent game in terms of our attention and chances created," he said of their last meeting.
"We must do this again on Tuesday night, whilst being cautious of their threat on the counter through the likes of Angel Di Maria, Cristiano Ronaldo and Gareth Bale."
"Plus, in Turin, we'll be able to count on the support of our fans, who will provide a red-hot atmosphere at the stadium.
"We haven't had a great deal of time in which to prepare for the game, but encounters like these provide plenty of motivation by themselves."