El Ahmadi was impressed with Sylla's powerful presence on the training field and his brief cameo debut at Goodison Park.
He told Villa's website: "Yacouba is the sort of player we need in this situation. He's a strong guy and a good player. He's more than welcome.
"It will be good for the team to have that competition in central midfield. I think both new signings are players we need at this moment in time.
"I think Yacouba is a good player. I faced him directly in some tackles in training and you can see he is a good player.
"He's a strong guy too and that is something we need."