Werder Bremen's Thomas Schaaf believes his side have to improve despite hitting FK Aktobe for six in the Europa League.

Bremen beat their opponents from Kazakhstan 6-3 at the Weserstadion, but the away goals they conceded are a source of concern for Schaaf.

"Every game brings its own dangers and I hope I see my team play better in the second leg," he said on the club's official website.

"The way in which we conceded the goals leaves room for improvement."

Schaaf also believes his team needs to be more ruthless up front.

"We regularly developed our moves going forward very well, but we have got to finish them off better," he added.

Claudio Pizarro made his first appearance for Bremen since sealing his permanent transfer from Chelsea earlier this week, but could not mark it with a goal.

Mesut Ozil and Naldo both scored twice for Bremen, while Hugo Almeida and Sebastian Boenisch were also on target.

But Pizarro too believes there is plenty of room for improvement, particularly at the back.

"If we had played like this against AC Milan last season, then we would have conceded more than three goals," said the Peruvian, whose two goals at the San Siro saw Bremen knock the Serie A side out of the UEFA Cup last year.

"We must still improve."