And Knill, who replaced Ian Baraclough as Iron boss at the end of March, will waste no time in his bid to steer his side straight back.
Knill said: "I'm hoping to be able to bring in five or six new faces during the summer.
"We've a number of players in mind who we would like to bring in, but there will also be interest from other clubs and it promises to be a difficult summer for us.
"The writing was on the wall as far as this season was concerned some time ago.
"All I asked of my players for this final game was to go out and give us a performance. I think we did that, but once again we were let down with what happened in the two penalty boxes.
"Ramon Nunez scored an excellent goal for us and we had some other good chances, but could not put them away.
"At the opposite end defending has always been a problem for us and it was always at the back of your mind that Portsmouth might get a late goal to deny us the victory I think we deserved."
He said: "David is out of contract and I have done everything I can to try and keep him at this club.
"There's nothing more that I can tell him that he does not already know.
"It's out of my hands now and I really don't know whether he will still be here next season."
Cotterill was relieved to have finished a difficult campaign well clear of relegation trouble.
He added: "We have done amazingly well to survive. Survival has been what it's all about for us this season.
"At the end of August when we were at the bottom of the table if someone had said we would finish with 58 points I would have snapped their hand off.
"That is what we have done, but I'm greedy, I want 68 and 78 points."
Cotterill is hoping that the club's ownership issue will be sorted out quickly this summer to enable him to bring new players in for next season.
"Until that happens there is little that I can do," he said. "It's difficult to lift the team at the end of the season when really our future was resolved about eight games ago.
"We were pretty rubbish in the first half and just had to improve in the second.
"We did that and I'm pleased that we sent our supporters home happy with at least a point."