"They have to start with a bang, with bat or ball."
Arnold acknowledged consistency isn't necessarily a feature of Sri Lanka's game but "they will show up at the right time".
"That's why they are good in these types of tournaments. If you expect them to win 10 games on the trot, that's not going to happen. They will do what is required [to get to the quarter-finals]."
At that point, Arnold said, Sri Lanka could step up a gear as they faced a series of one-off, knockout games.
When Sri Lanka's cup campaign is over, it will also be the end for two of their true champions, Mahela Jayawardene and Kumar Sangakkara. Sri Lanka will be praying for plenty from the batting rocks on whom their hopes of success rest.
Arnold drew a parallel with the issues of maintaining a quality bowling attack once Muttiah Muralitharan and current team bowling coach Chaminda Vaas retired.
"Certainly it will be challenging. You cannot replace that experience and quality just like that.
"There is a lot of hope and excitement among the Sri Lankan lads, but let them grow in their own way. That way we'll move forward much faster."
As a former teammate of Jayawardene - who is retiring after the Cup - and Sangakkara, for whom the international sunset will arrive in the next couple of months, Arnold drew distinctions between the two good friends.
They are third (Sangakkara) and fifth on the ODI runmaking list with 13693 and 12525 runs respectively and 39 hundreds between them.
"When Mahela was a youngster, 14 or 15, I came across him in school cricket and even at that stage people would say 'here's a guy to watch in the future'.
"That wasn't the case for Kumar. He matured much later.
"Mahela is total flair and someone who would rely on his skill to get him through.
"Kumar is a professional. He needs to hit a million balls and his preparation has to be spot on. He is the ultimate machine.
"Mahela can be crap in the nets the day before, then turn up and go about his business. If Kumar does not get his perfect net it can be a worry for him."
Character-wise, Arnold said there were also differences.
"Mahela is more organised. He's on time. If he tells you he'll do something he will do it.
"But Kumar is a scatterbrain, never on time, totally disorganised," he laughed. "But when it comes to doing it, he's spot on."
On these men, and the likes of captain Angelo Mathews and key bowler Lasith Malinga, Sri Lanka's hopes rest.
For more coverage of the Cricket World Cup from nzherald.co.nz and NZME. check out #CricketFever.
