The battle for control of Champions League Group F match begins in earnest on Wednesday when AC Milan host Barcelona at the San Siro stadium.
After two games both sides have a maximum six points, having beaten Shakhtar Donetsk and Celtic in their opening games, though the manner of their respective victories could not have been more different.
The Italian champions made a sluggish start. Having edged out Shakhtar 1-0, they then needed two late goals to see off Celtic 3-1.
In Serie A, meanwhile, they suffered their first home league defeat of 2004 in going down 2-1 to promoted Messina and are only belatedly rediscovering their form.
Sunday's 1-0 victory against Cagliari lifted them to second in the division behind Juventus but the game against Barcelona promises to be their toughest test of the season so far.
Coach Carlo Ancelotti has a full-strength squad at his disposal, including striker Filippo Inzaghi, who is expected to return to the starting line-up after recovering from an ankle injury.
The 31-year-old striker came on as a sub to score the vital second goal in Milan's win over Celtic.
In contrast to six-times former European champions Milan, Barcelona have got off to a flying start in both domestic and European competition.
The Catalan club, thrashed 4-0 in the 1994 final by Milan, stretched their lead at the top of the Spanish Primera Liga to five points at the weekend following a comfortable 1-0 win over city rivals Espanyol and are now the only unbeaten side in the league.
They won their opening two Champions League matches against Celtic and Shakhtar Donetsk by comfortable margins and still look to be playing well within themselves.
ButAfrican Player of the Year Samuel Eto'o, who has been in outstanding form since joining the club from Mallorca in the close season, believes the team need to make sure they do not get carried away by their early success.
"Wemust make sure we retain the humility that has served us so well up until now," the Cameroon striker said on Monday.
"Thegame against Milan is a very important one, but we need to stay calm and concentrate as much as possible on the task in hand."
Theonly blot on the landscape for coach Frank Rijkaard has been the string of injuries that have hit the squad in the opening weeks of the season.
DefendersGabri and Edmilson and midfielder Thiago Motta are all out for around six months with serious knee injuries.
Leftback Silvinho is still recovering from a knee problem and midfielder Gerard and French winger Ludovic Giuly have been sidelined with muscle injuries.
Thegood news for Rijkaard is that inspirational fullback Carles Puyol looks to have shaken off a minor knee injury and should play against the Serie A side.
AC Milan: 1-Dida; 2-Cafu, 13-Alessandro Nesta, 31-Jaap Stam, 3-Paolo Maldini; 8-Gennaro Gattuso, 21-Andrea Pirlo, 20-Clarence Seedorf; 22-Kaka; 7-Andriy Shevchenko, 9-FilippoInzaghi.
Barcelona: 1-Victor Valdes; 2-Juliano Belletti, 5-Carles Puyol or 19-Fernando Navarro, 23-Oleguer, 12-Giovanni van Bronckhorst; 20-Deco, 6-Xavi, 4-Rafael Marques; 10-Ronaldinho, 7-Henrik Larsson, 9-SamuelEto'o.
Referee: Graham Poll (England)
(Additional reporting by Simon Baskett)