The 21-year-old signed a season-long loan deal with the Bees on transfer deadline and has used the international break to impress head coach Dean Smith further.
Walsall full back Rico Henry signed a five-year deal the same day, but a shoulder injury means he must wait to make his first start for his new club.
But Smith insists the pair have the potential to be key signings for his ambitious Championship club.
“Sullay and Rico are both young lads and they are gaining experience just by being around the players,” said Smith.
“Rico is injured so he has been in the treatment room but he is having lunch with the players and mixing in.
"Sullay has mixed in really well and he has been impressive in training so far.
"I am pleased with those acquisitions and hopefully in the long run they can prove to be really good signings."
Brentford head to the Amex Stadium tomorrow hoping to be the first team to come away from the Seagulls with maximum points this season.
Last year’s play-off semi-finalists have won both their home games 3-0 this campaign, the same scoreline they beat The Bees by last February, but head coach Smith feels his team can be the ones to end that run.
Fit again: Alan McCormack has recovered from injury and could face Brighton tomorrow
“It will be a tough game on Saturday,” he added.
"They were very unfortunate to miss out on the last game of last season after a fantastic season.
"I know Chris Hughton and Colin Calderwood and they have a very good squad of players there. They are strong and organised and it will be a tough game.
"I watched them play Nottingham Forest and they beat them 3-0 and they beat Rotherham United 3-0.
"It is quite daunting that they have played two home games and won both of them 3-0. We will give them a lot of respect but we don’t fear them and we are more than capable of competing and giving them a really good game.
"We didn’t perform well there last season but we had a lot of injury problems at that time. We will be going there with a near enough full squad and thoughts won’t be on last year, they will be on this year.
Back: Yoann Barbet played for the Brentford B team against Liverpool last night at Griffin Park
"We have got new players in our building and they have got new ones in theirs so it will be a good game.”
The Championship had a break from fixtures last weekend as 2018 World Cup qualification began and Smith admitted it was a welcome chance to get his squad fully fit after a hectic start to the campaign.
Both Alan McCormack and Yoann Barbet are back in contention to feature this weekend
“We worked really hard over the international break, had the weekend off to recharge the batteries, and spend some time with the families,” Smith said.
“Now the players are really looking forward to the six games before the next break.
"Ryan Woods felt his thigh in the Sheffield Wednesday game and Nico Yennaris had a hip problem but they have come through that now and they are fully training."