Afghanistan skipper Hashmatullah Shahidi won the toss and chose to bat against Sri Lanka as they looked to clinch the series in the third one-day international on Thursday.
The tourists lead the three-match series 1-0 after winning the opener and after the second match was washed out in Pallekele.
They have made one change from the rained-off match, with debutant Noor Ahmad coming in for Yamin Ahmadzai.
The Afghans earned a direct qualification for next year's ODI World Cup after they and the hosts took five Super League points each on Sunday.
Sri Lanka's chances of automatic qualification for the tournament took a serious hit as they lie 10th in the Super League points table.
World Cup hosts India and seven other top teams will gain direct entry to the tournament.
Sri Lanka made two changes, with Dunith Wellalage and Asitha Fernando replacing Dhananjaya Lakshan and Lahiru Kumara.
Teams
Sri Lanka: Pathum Nissanka, Kusal Mendis (wk), Dinesh Chandimal, Dhananjaya de Silva, Charith Asalanka, Dasun Shanaka (capt), Wanindu Hasaranga, Dunith Wellalage, Maheesh Theekshana, Asitha Fernando, Kasun Rajitha
Afghanistan: Ibrahim Zadran, Rahmanullah Gurbaz (wk), Rahmat Shah, Hashmatullah Shahidi (capt), Najibullah Zadran, Mohammad Nabi, Gulbadin Naib, Rashid Khan, Mujeeb Ur Rahman, Noor Ahmad, Fazalhaq Farooqi
Umpires: Lyndon Hannibal (SRI), Nitin Menon (IND)
TV Umpire: Raveendra Wimalasiri (SRI)
Match Referee: Ranjan Madugalle (SRI)