The 23-year-old Frenchman, who arrived at the club from Clermont Foot at the start of 2013, has made just 13 appearances for the Villans this term.
Sylla recently admitted that he was disappointed by his lack of first-team action at Villa Park.
"I understand people's frustration at not playing," Lambert told the Birmingham Mail. "I think that's normal at any football club. You wouldn't expect people to want to sit there and not play.
"I think that's normal so you're glad in that respect. Should he have spoken out? Probably not, but that comes with experience and I'm glad he's feeling disappointed at not playing."
Villa continue their fight for Premier League survival on Saturday at home to Hull City.