The Welsh international said: "Tony Mowbray is the man to take the club forward without a shadow of a doubt. He is a pleasure to play for. I've enjoyed every single training session we've had this year. He is so positive. If people are knocking him, they need to have a look at themselves. He has been great for me. It has been a pleasure to play for him. He is a great fellow off the pitch as well. People tell me some fans are saying we are negative. It hasn't been negative. Look how many goals we've scored. I think we've scored more goals than anyone in this division. We've been unlucky. We had a bad spell in March which cost us big-time. We had chances against Derby and they've scored from one breakaway. It sums our season up to be honest. It is devastating. We should have been celebrating afterwards, not them. It feels like it has been a waste of a season, coming this far and getting beaten by them. It's hard to take."
The 27-year-old has had an outstanding season after going AWOL from West Brom last summer and several Premiership clubs, including Everton, are understood to be interested in the player.
Koumas said: "What about my future? I've no idea. I've a big game for Wales on Saturday and then I'll have a nice break and think about what I am going to do. I don't know what my future holds because I'm at an age where I want to step up. It's been too long in waiting. I'm desperate to play in the Premiership but it's up to the chairman. We'll have a talk and see what happens. The season has gone well for me but it makes no difference with what happened on Monday."
Skipper and central defender Curtis Davies, top scorer Diomansy Kamara and left-back Paul Robinson could all be targets for Premiership clubs during the summer in addition to Koumas.