Cape Town - It's a matter of when, not if, Sri Lanka get the injection of confidence they need to ignite their Cricket World Cup campaign.

That's the view of Jeevan Mendis, who watched on as his side fell to a ten-wicket defeat in their opening game against New Zealand in Cardiff.

Mendis - returning to the fold four years after his ODI debut - feels with eight games still to play that Dimuth Karunaratne's men can still get the wins they need to advance to the final four.

"We have to say the first two games are very crucial to give all the players and the team a boost," said the 36-year-old.

"We hope we can pull something out of the bag in the next games.

"The format is good. For all the teams to play each other is great and it gives us lots of chances to get the five wins you need to get to the semi-finals.

"As a batting group, we need to at least put scores of 270, 280 on the board. Hopefully the wickets dry up and our pace and spin variation come into play.

"It's all about our confidence and a few batsmen can get in and play an anchor role, we'll be able to bat around them and play well."

Sri Lanka will remain in Wales with their next World Cup outing coming against Afghanistan, the only World Cup contender ranked lower than them in the ICC rankings.

They'll need to kick the habit of losing wickets in the first ten overs if they're to continue their fine record at ICC major events, reaching the knockout stages in eight of the last nine showpieces.

Mendis reiterated head coach Chandika Hathurusingha's emphasis on keeping wickets in hand early on, allowing the powerful likes of Thisara Perera and Isuru Udana to cut loose in the closing overs.

"We always talk about not throwing too many wickets away in the first powerplay, but it didn't happen," Mendis said.

"We always want to score 30, 40 runs in the first powerplay and not lose too many wickets.

"New Zealand bowled well and were very disciplined, so it became a sticky innings for us.

"We need to adapt to score runs at all stages of the innings.

"We have power hitters who can come in at the latter stage and make quick runs so hopefully the top five can put us on a good platform."