The pair have been absent from recent pre-season friendlies with differing injuries but both have been training this week and will be in the travelling party for the trip to Yorkshire.
He said: “Nico has trained all week. He is fully fit and has made himself available for the game.
“Alan McCormack has trained all week. He's a little behind Nico but he's available as well.”
Yennaris could be drafted in at right back with Maxime Colin unlikely to make the trip, although he has a chance to force his way into Smith's thinking on Friday.
He added: “Maxime is touch and go with a calf injury. We'll assess tomorrow and see if he's up to travel or not.”
Andreas Bjelland definitely misses out and the Brentford head coach is unsure when he will have him available to make his league debut for the club after missing last season with an anterior cruciate ligament.
He explained: “I haven't pencilled Andreas in for a game. He's not training with me yet.”