Sri Lanka's teenage spinner Dunith Wellalage has been included in the final 12 for the second Test against Pakistan in Galle, skipper Dimuth Karunaratne said on Saturday.

The 19-year-old Wellalage, a left-arm orthodox who awaits his Test debut, seems a likely replacement for injured spinner Maheesh Theekshana as the hosts look to bounce back in the two-match series after their opening loss.

"Dunith Wellalage is back in the squad" after being released from the Test squad for a domestic match, Karunaratne told reporters.

"Asitha Fernando is back in the 12. Those are the only changes," he added on the eve of Angelo Mathews' landmark 100th Test starting Sunday.

Wellalage, also handy with the bat, played a key role with his nine wickets in Sri Lanka's 3-2 one-day series win over Australia last month, and could partner with Prabath Jayasuriya in the final Test.

Pakistan rode on opener Abdullah Shafique's unbeaten 160 to chase down a record 342 at the Galle International Stadium on a tense fifth day to go one up.

Jayasuriya waged a lone battle with his left-arm spin to claim a match haul of nine wickets, but found little help from the other end.

"We did pretty well in the first Test but the conditions were not to our assistance," said skipper Karunaratne. 

"Another area that we need to work on is first innings batting."

Pakistan added left-arm spinner Nauman Ali to the team announced Saturday, in place of injury-hit pace spearhead Shaheen Shah Afridi.

Shaheen claimed four wickets in the first innings of the opener and coach Saqlain Mushtaq said he would be missed.

"He is inspirational, leads the bowling unit from the front, and we will miss his aggression and his presence," he said. 

"The way he comes and gives us the breakthrough at the start... hopefully the other bowlers will step up."

The pitch at Galle has changed character in all three matches played in the past few weeks, including two Tests against Australia.

Sri Lankan players believed the pitch went flat on the final two days when Pakistan batted, but Saqlain said his batsmen were up to the task.

"I believe the pitch turned from day one and it kept spinning, but I think our boys showed some really good character in this match," said the former off-spinner.

"It was a show of determination, patience and temperament by our players."

Sri Lanka 12: Oshada Fernando, Dimuth Karunaratne (capt), Kusal Mendis, Angelo Mathews, Dinesh Chandimal, Dhananjaya de Silva, Niroshan Dickwella (wk), Ramesh Mendis, Dinuth Wellalage, Prabath Jayasuriya, Kasun Rajitha, Asitha Fernando

Pakistan XI: Abdullah Shafique, Imam-ul-Haq, Azhar Ali, Babar Azam (capt), Salman Ali Agha, Mohammad Rizwan (wk), Mohammad Nawaz, Yasir Shah, Hasan Ali, Nauman Ali, Naseem Shah