Silvio Berlusconi's younger model AC Milan face ultimate scrutiny from Barcelona in the Champions League

Reshaped Milan side aim to 'sterilise' Catalans at San Siro – and boost president's election aims

For five seasons football's greatest coaches have pondered the almost impossible task of stopping Barcelona. According to Silvio Berlusconi the key is to man-mark Lionel Messi. That was the advice the former Italian prime minister gave his coach Massimo Allegri before Milan's meeting with Barça at San Siro.

The last-16 first leg pits the belle of the ball against the team who were given a huge facelift in the summer, and it had stirred an old penchant for coaching football teams in the 76-year-old businessman and politician – apparently he used to coach his sons' side and they never lost a game.

That Milan facelift has taken years off the side that took on Barcelona twice last season in the group stage of the competition with an average age of 30. Tomorrow it will be put to the strongest possible test.

Eleven players who played in at least one of the two games between the two teams last season were sold by Milan in the summer. Of those who left the club only Alexandre Pato and Thiago Silva were under 30 and the team's average age has dropped to 27.

Allegri is unlikely to pay too much attention to his president, who will be in Rome ahead of the upcoming Italian elections, but an ultra-defensive performance to limit Barcelona's away goals tally is highly likely. "Barcelona always end the game with at least 65 per cent of possession – we have to make them sterile", said the Milan coach.

The Barcelona coach, Tito Vilanova, is still in New York receiving medical treatment so his No 2 Jordi Roura will again take his place on the Barcelona bench. For Roura it's a return to the stadium where he tore cruciate ligaments in a 1989 Super Cup match effectively bringing to a premature end his Barcelona playing career.

Barcelona have reached the semi-finals of the competition in each of the last five years and won the trophy twice in that period. Tomorrow Messi reaches another landmark. Fresh from scoring his 37th league goal of the season at the weekend, he plays his 75th Champions League game, just over eight years after making his debut in Donetsk on 7 December 2004. Three European Cups and 56 Champions League goals later the player who has four times finished as top scorer in the competition will be the biggest threat to Milan.

Without the cup-tied Mario Balotelli, Milan will have Stephan El Shaarawy, who has shaken off injury, and Kevin-Prince Boateng playing behind Giampaolo Pazzini. Bojan Krkic, who broke goalscoring records as a youngster at Barcelona before failing to establish himself in the first team and having to move to Italy to further his career, will be asked to make an impact from the bench.

Barcelona left David Villa at home after his kidney stone problems last week. Messi will be flanked by Andres Iniesta and Pedro in attack with Xavi Hernandez returning in midfield after two games out, alongside Cesc Fabregas and Sergi Busquets. Xavi scored a winner in the group game between these sides last season – back before Berlusconi had traded his old Milan in for a younger model.

Kick-off 7.45pm, San Siro

TV Sky Sports 2 Referee C Thomson (Scot)

Odds Milan 5-1. Draw 3-1. Barcelona 8-15.