The 20-year-old left-arm medium-pacer Madhushanka has also sustained a hamstring injury.
Interestingly, Madhushanka was not in the playing eleven in the first Test but he sustained the injury during training two days prior to the first Test.
Both left the Bio-Secure Bubble (BSB) and team hotel on Monday; it is learnt here.
The 24-year-old right-arm fast bowler Lahiru has a history of getting injured during the middle of the series and was partially out of the first Test because of the injury.
"He (Lahiru) needs no surgery and can be managed with the rehabilitation", the source close to the team management said on Monday morning.
The selectors have added two members to the squad. Chamika Karunaratne and Lakshan Sandakan will be joining the team squad on Tuesday.
The 25-year-old fast bowler Karunaratne and left-arm spinner are in Colombo now. Their PCR tests are negative and they will now give antigen body tests before joining the squad.
Usual health protocols will be followed for their inclusion in the team.
The second Test of the Walton Series begins on Thursday at the same venue.
The pitch for the second Test is likely to be different than the one where the first Test was played and ended in a dull draw.