The 18 year old joined the Bees on deadline day in an initial £5n deal which could potentially rise to £10million after being in the final year of his contract.
Martin has said he would have liked to keep the England youth international, but Brentford’s offer was too good to reject.
"Our preference would have been Jayden accepting the contract that we offered, which was a really good one for a player of his age.
"He played a good few games for us last season - more than most players of his age in Europe in his position.
"Jayden has gone somewhere where he thinks he might get more opportunity earlier. I disagreed with him but we will have to wait and see.
"The club received a really good price. It's really good business for the club to make a big profit on him at an early age.
"I hope he goes on to have a really brilliant career because he is a top talent, an excellent player and a really good young man."
Despite the disagreement over game time, Martin wishes all the best for the teenager who hopes to find regular chances at a Premier League rival.
"He goes with everyone's best wishes. Hopefully he enjoys himself and does what he wants to do there.
"Albeit, it's a bit frustrating for us as coaches to not be able to work with him further. We couldn't have done any more as a club.
"So, at that point, if someone isn't going to sign a new contract then you try and get the best deal that you can. I think Rasmus, Phil and the gang have done a brilliant job in doing that.
"I think it shows young players that there is a pathway here and a platform to go on and do something else. It's a good move for Jayden, a good move for us and everyone can move forward."