"You must do your job with your players after the season has ended and in the summertime you need to do your job with your staff," he said.
"The key, though, is to sign the right players with the right mentality - a winning mentality - competitive players, players who are desperate to come here to win something.
"That is the key for me. We have been analysing a lot of things this summer. For example, we were conceding a lot of goals last season from set pieces.
"We need to know why because the previous season we only conceded six, but this year it has been 16. We need to know why so we can improve in these areas, but keep the team scoring goals in open play.
"We have been really good in defence for three or four years but we need to improve a little bit if we want to be in contention."