Lionel Messi is battling to be fit for Barcelona's trip to Rubin Kazan on Wednesday but if injury keeps him out a host of other forwards are waiting in the wings to borrow his crown as Champions League king.

The little magician, inspirational in Barca's 2009 triumph and run to the semi-finals last term, has missed two league games with ankle ligament damage but could return against a side who shocked Pep Guardiola's men last season with a win at the Nou Camp and a goalless draw in Russia.

Messi scored twice in the 5-1 home victory over Panathinaikos in Barca's first Group D game two weeks ago when former team-mate Zlatan Ibrahimovic also bagged a brace for new club AC Milan.

Ibrahimovic, cast aside by Guardiola after failing to come out of Messi's shadow, netted a double in Milan's nervous 2-0 win over Auxerre in their Group G opener at the San Siro and has since scored twice in Serie A to warm up nicely for Tuesday's second match at Ajax Amsterdam.

"I've scored four goals so far, all of them were important. I don't know which one was the most beautiful, we should ask the fans," the Swede told reporters before giving an ominous warning for Europe's defenders.

"I'm still not fully fit, but I'll be at 100 per cent soon. Like I said on my first day at Milan, I came here to win," he added.

Another former Barcelona striker, Samuel Eto'o, is in excellent form for holders Inter Milan and was unlucky not to score again in Saturday's 1-0 defeat at AS Roma in Serie A.

A first Champions League home game as Inter boss awaits Rafael Benitez in Group A on Wednesday when Werder Bremen come to town hoping to exploit set pieces just like Twente Enschede did in their opening 2-2 draw with the treble winners.

Diego Milito, who scored both goals in last May's final when Inter overran Bayern Munich, still has to fully rediscover his touch in front of goal but Benitez's lack of options mean the Argentine has to play practically every game.

Four-times winners Bayern, who visit FC Basel in Group E on Tuesday, are a long way from the form, which took them to last season's final as underlined by Saturday's 2-1 home defeat by Mainz 05.

Creative wingers Franck Ribery and Arjen Robben are injured so the burden may again fall on World Cup Golden Boot winner Thomas Mueller, whose wonder goal set up a 2-0 win over AS Roma last time out in Europe.

While Mueller was wowing the crowds in South Africa, Cristiano Ronaldo and Wayne Rooney were big disappointments and their club seasons have yet to really spark to life.

Ronaldo's Real Madrid were held to a 0-0 draw by promoted Levante on Saturday but the Portuguese was their liveliest attacker and will now try to unleash his frustration at Auxerre on Tuesday.

"Our tactics aren't the problem, but we aren't scoring," Real boss Jose Mourinho said.

"It's not because of our players because we all know just how capable they are of scoring, but we aren't right now. That is my only worry," he added.

The struggles of Manchester United's Rooney may also be troubling Alex Ferguson with another lacklustre display in a 2-2 draw at Bolton before Wednesday's Group C trip to Valencia.

Fellow English side Chelsea lost their first league game of the season on Saturday against Manchester City but should have an easier time at home to Marseille in Group F on Tuesday, with Didier Drogba keen to remind his old club of his strength.