Pakistan captain Misbah conceded Malinga could be vital.
"Malinga is a very good bowler, he makes a difference and everyone knows he is a good bowler," said Misbah on Thursday. "We have played very well against him but they have an edge with him in the side."
Pakistan won the preceding three-Test series 1-0 when Sri Lanka were without Malinga who retired from Test cricket earlier this year because of persistent injury problems.Dilshan said Malinga, who has 149 wickets in 94 one-day internationals, is an asset for his team.
"Lasith is one of the assets for Sri Lanka," said Dilshan. "He is one of the great bowlers in the world and he can guide other bowlers as well and his comeback in the series is a good sign for the team."
Malinga was also sidelined with injury when Pakistan beat Sri Lanka in the group match in Colombo in this year's World Cup.
But once Malinga returned, Sri Lanka finished runners-up to India. Pakistan lost to India in the semi-final of the World Cup.
Pakistan were boosted by the return of allrounders Shahid Afridi and Abdul Razzaq who both had turbulent periods since the World Cup.
After the West Indies series in May, Afridi fell out with then coach Waqar Younis before being sacked as one-day captain. In protest he retired from international cricket and only took back his decision last month.
Razzaq was sidelined after a poor World Cup, but was recalled after he led Pakistan to Super Sixes title in Hong Kong earlier this month.
And Misbah hoped both the allrounders give Pakistan more strength.
"Both Afridi and Razzaq give strength to our team," said Misbah, who was appointed captain for all three formats in June this year. "We know Sri Lanka are a good side but we are ready for them."
Dilshan also hoped his team remain focused and win the series.
"We know we have not won a series since the World Cup, so the players are determined to put that behind and play our brand of cricket to win the series," said Dilshan, who took over from Kumar Sangakkara after the World Cup.
Sri Lanka need to win 4-1 or better to keep their second place in the ICC (International Cricket Council) one-day rankings intact. They drop one place even if they win 3-2.
On the other hand Pakistan jump fifth to their current sixth place if they win 4-1 and in case they win 5-0 they go to fourth.