Brentford's Nico Yennaris knows first hand the challenge of stopping Chelsea's Cesc Fabregas.The pair were briefly team-mates at Arsenal and are expected to be in direct opposition in Saturday's FA Cup fourth-round tie at Stamford Bridge.Spaniard Fabregas left for Barcelona before Yennaris could really learn from the World Cup winner.But the one thing that sticks out from training with Fabregas for lifelong Arsenal fan Yennaris was his passing."Not any one moment, but his passing range and his vision is second to none," said the 23-year-old, who made three first-team appearances for the Gunners before leaving in 2014."Given time and space he can pick a pass. We'll have to try to stop that."We trained together there a few times, just before he left for Barca. I know a bit about him."It will be good for me to test myself against players of his calibre."We all know the qualities he has and how good a footballer he is. It will be a good test for myself. "I'll try to remember the things he used to do in training a lot."I definitely have to be on my game."Yennaris' Arsenal connection means he will be keen for Brentford to emulate Bradford, who in 2015 beat Chelsea in the FA Cup fourth round."When I saw the draw and tweeted it a few Arsenal fans tweeted me and said 'you've got to do them over'," he added.Yennaris says the uncertainty over the future of top-scorer Scott Hogan has had no impact on his Brentford colleagues.Hogan has been linked with a move to West Ham before Tuesday's transfer deadline, but so far interest has fallen short of the Bees' £15million valuation.Yennaris said: "We've been in this situation before with players leaving and speculation of interest from other clubs. The players have just got on with the job."It happens all the time in football so we're used to it. The boys have just blocked it out and focused on the next game ahead."The next game for a side placing 15th in the Sky Bet Championship, after losses to Newcastle and Wigan, is a local derby against Chelsea, their opponents at the same stage four years ago. Brentford were beaten 4-0 in the replay after drawing at Griffin Park in 2012-13."People probably expect Chelsea to win the game," Yennaris added."We've just got to go to enjoy it, play without pressure and play with freedom."The FA Cup is full of surprises."Head coach Dean Smith reported a full contingent trained on Thursday seeking to be selected for Stamford Bridge.Hogan could be left out, given he has not featured for three weeks due to being rested and the speculation over his future.