The prospect of an unprecedented Champions League final between bitter rivals AC Milan and Inter Milan is at stake as the Serie A giants attempt to negotiate awkward quarterfinal ties Tuesday.
The Italian giants have regularly crossed swords in Europe's premier club competition, with last season's controversial quarterfinal which ended in defeat for Inter being the most recent encounter.
But wins for Milan and Inter over Lyon and Villarreal respectively will leave the two teams from northern Italy only a semifinal away from a dangerous liaison in the May 17 final in Paris.
Both teams are narrow favourites to progress to the last four going into Tuesday's second legs, but neither will be taking anything for granted.
Milan coach Carlo Ancelotti shrugged off his team's shock 1-0 defeat to lowly Lecce in last weekend's league fixtures, a result that has effectively killed off their faint hopes of catching leaders Juventus.
Ancelotti said he was not bothered by his side's display, and is confident they will bounce back against Lyon, who held the Italians to a goalless draw in the first leg.
"It's just a bump in the road," Ancelotti said of the Lecce loss.
"However, in the Champions
League, we will be different. I am optimistic, but we must play a great game to get through."
Milan are desperate to win the Champions League after their heartbreaking defeat to Liverpool in last season's final in Istanbul.
The six-time European champions threw away a 3-0 lead to draw 33, before losing on penalties.
Andriy Shevchenko, Kaka and Gennaro Gattuso were rested against Lecce, but all are expected to start on Tuesday.
Dutch defender Jaap Stam has recovered from a calf strain and is likely to return to the right-hand side of Milan's defence.
Lyon, who beat Troyes on Saturday to extend their lead at the top of the French first division to 12 points, welcome back Juninho from suspension, but Portuguese midfielder Tiago will serve a one-match ban.
Lyon keeper Gregory Coupet believes the return of Brazilian playmaker Juninho could be the key to winning the tie.
"At 0-0 we have hope, although the hardest part is ahead of us," he said.
"Juninho will give an edge to our attack that we didn't have in the first leg. Milan will have to avoid giving away free-kicks because he is an expert in dead-ball situations."
The winner of Tuesday's match will face a semifinal with either Barcelona or Benfica, who play Wednesday.
Inter defend a 2-1 first leg lead when they travel to Spain to play
Villarreal, arguably the surprise package of this season's tournament.
While Inter's famous teams of the 1960s wrote the book on defensive football, Serbian midfielder Dejan Stankovic has warned his teammates not to fall into the trap of sitting on their first leg cushion.
"There's so much at stake, it would be foolish to go there and try and protect our lead," Stankovic said. "A 1-0 win would be a good enough result for Villarreal, so it would be a risky game for us to play.
"But if we can score, then that will leave them needing three goals to go through. So we have to go there with a positive attitude."
Villarreal, nicknamed the 'Yellow Submarines', hail from a small industrial town of around 50,000 people and have spent most of their existence toiling away in Spain's regional leagues.
But since elevation to the Primera Liga, Villarreal have enjoyed phenomenal success given their limited resources and are within touching distance of a place in the Champions League last four.
They have already claimed the scalps of Manchester United and Rangers during this campaign, and warmed up for Tuesday's Inter tie by beating Real Zaragoza 1-0 away on Saturday, their first win in five matches.