Sri Lanka trimmed their provisional 18-man squad down to 15 with Vaas joining skipper Marvan Atapattu and Ruchira Perera on the injured list.
Vaas, Sri Lanka's senior fast bowler, is now targeting a return in the second Test in Kandy that starts on April 3 but Sri Lanka's team management have made it clear they will not risk him if there is a chance it could aggravate the injury.
''We do not want to risk Chaminda (Vaas) unless he is 100 percent fit,'' Sri Lanka coach Tom Moody told reporters after the team's training session today.
Atapattu has a lower back injury and left-arm fast bowler Perera is recovering from a hamstring pull.
Veteran Sanath Jayasuriya, Sri Lanka's highest run scorer in Tests and ODIs, looks set to make a return from a thigh injury and will open the innings with fellow left-hander Upul Tharanga.
Sri Lanka's main selection dilemma is whether to play a specialist batsman at number seven or an all rounder like Farveez Maharoof who fulfilled that role successfully against Bangladesh earlier in the month.
Apart from Vaas, fast bowler Dammika Prasad and opening batsman Ian Daniel have been left out of the final 15-man squad.
Sri Lanka will face a tough time against a confident Pakistan team that recently won a three-match ODI series 2-0.
New captain Mahela Jayawardene said his players have put the disappointment of losing the One-day series behind them and are looking forward to the challenge of the Test series.
''The One-day series is gone and we cannot dwell on that,'' Jayawardene told Reuters.
''The challenge is to learn from the mistakes and build on the positives, which we have been focusing on doing in the last few days,'' he added.
''Crucially, the senior batsman like myself, Sanath (Jayasuriya) and Kumar (Sangakkara) need to shoulder responsibility so that our bowlers are able put Pakistan's top order under pressure.'' Despite Sri Lanka's injury woes, Pakistan skipper Inzamam-ul-Haq insists the tourists will not be taking their opponents lightly.
''The one-dayers are history now and we must make a fresh start,'' Inzamam told reporters.
''Some of Sri Lanka's top players are injured but they have a great record on home soil and we are going to have to work really hard to beat them in this series,'' he added.
Off spinner Arshad Khan has joined the squad after missing the one-dayers but leg spinner Danish Kaneria remains the likeliest choice if Pakistan go into the match as expected with just one specialist slow bowler.
Although Shoaib Akhtar is missing after knee surgery and Mohammad Sami has been axed, Pakistan's pace attack remains potent with Rana Naved-ul-Hasan, Mohammad Asif and Umar Gul all likely to play.