Ryan Jarvis opened the scoring from the edge of the penalty area in the 37th minute before Sam Wood’s 76th-minute leveller and a late winner from Matt McClure.
Knill said: “I am delighted we scored after such a long time waiting for a goal, but I’m obviously disappointed that we could not keep hold of that 1-0 lead for a win.
“I have got to say it’s quite difficult and we are all quite sure that with more concentration it will quickly turn for us.
“We weren’t happy at half-time. Even though we were leading 1-0, it probably took us 25 minutes or more to get going.
“I think there is a touch of apprehension. We have got some young players and they probably haven’t been in this situation before and it took at least half an hour to get us going.
“Within that opening half an hour they were fantastic at defending corners, because we had to defend quite a few, and then all of sudden we got the goal and there was a game on.
“For a while we looked as good as them. I thought we finished the half better. Then, in the second half, we had a great chance, didn’t take it, and they go down the other end and we concede the goal, and you can see us go deeper and concede again.
“Instead of stepping forward we stepped back and I have seen it before. We will show the players what is going wrong and hopefully put it right on Saturday.”
Southampton have announced plans for a two-week tour of China as part of their pre-season preparations for the 2018-19 season.