Lionel Messi's brilliance has helped Barcelona keep pace with La Liga leaders Real Madrid in recent weeks but the champions are still waiting for striker Zlatan Ibrahimovic to justify his expensive price tag.

Messi netted a second hat-trick in a week in Barca's 4-2 win at Real Zaragoza on Sunday, taking his tally to 11 goals in five matches, before generously allowing Ibrahimovic to take a late penalty that ended the Swede's month-long scoring drought.

Ibrahimovic moved from Inter at the end of last season in a swap deal that valued him at around €66 million but before Sunday had not scored in the league since mid-February and has 13 league goals to Messi's 25.

"Ibra is a bit down but the penalty gave him a lift," defender Maxwell told reporters.

"We are all standing by him and we know he is a great goalscorer," the Brazilian added.

Barca, who are level on 68 points with Real but have an inferior goal difference, can go three points clear at the top with a win at home to Osasuna tonight.

Coach Pep Guardiola could be without central defenders Gerard Pique and Gabriel Milito for the clash at the Nou Camp after Pique damaged his knee in Zaragoza and Milito picked up a calf problem.

Guardiola said he believed Ibrahimovic was getting back to something like the form he showed at the start of the campaign.

"He took a step forward on Sunday. He was involved a lot," he told a news conference.

"We will be relying on him a great deal during the remainder of the season."

Real play at city rivals Getafe tomorrow and midfielder Rafael van der Vaart said they would probably need to win their remaining 11 matches, including the "Clasico" against Barca in three weeks, to take the domestic title.

"The league is our only chance of silverware now and we want to win it whatever it takes," the Dutch international said in an interview in As sports daily.

"We'll have to see how Barca respond but we are confident," he added.

Valencia, 18 points behind the top two following their 2-0 win over Almeria, host Malaga today.