Both players signed for the West Midlands club on transfer deadline day and Lambert believes that they can bring "freshness" to a team that is battling to avoid relegation to the Championship.
"I think new faces do give you a lift. As soon as they come in, they bring freshness to anybody," the Birmingham Mail quotes Lambert as saying. "I spoke to them the other day and they are both raring to do well.
"I wouldn't have any fear about throwing them in, whether it is against Everton or West Ham next weekend.
"I've seen them both play so we know exactly what we're getting. They're young players but they'll give it everything they've got for this club and that's what you need."
Sylla and Hawkins could feature against Everton on Saturday.