Gul, who has played just eight One-day internationals and four T20 matches for Pakistan since having a knee surgery in Melbourne in May last year, said he was frustrated at being plagued by fitness issues.
"It is frustrating and right now the doctors and trainers at the national cricket academy have told me I am still not 100 per cent fit and need to do more rehabilitation and gym training so that the knee is back to normal," Gul said.
Gul, 30, who is the most experienced pace bowler in the present team with 163 Test, 173 ODI and 80 T20 wickets, was sidelined for the ongoing series in Sri Lanka because of fitness problems.
This after he struggled with his knee during comebacks to the team for the ODI series against Sri Lanka in the UAE in January and then in the Asia Cup and T20 World event in Bangladesh in March-April.