Koeman has insisted that the club still has business to do before the summer transfer window shuts at the end of this month.
The Blues' manager said: “We still need to sign a striker. Everybody knows that we lost Romelu Lukaku. We brought in Wayne Rooney, Sandro Ramírez and now Gylfi, and maybe they can share the goals around more than happened last season, but we still need another one to play the No9. When you play in Europe, and let’s hope we reach Europe, and in the Premier League you cannot do it with just one or two strikers.”
Everton's current summer spending stands at £131m but Koeman hopes there is more to come. The Toffees were linked with Arsenal striker Olivier Giroud last month but Koeman believes that this deal is no longer possible with the French forward making his peace with Arsene Wenger.
He also admits that without Champions League football it is hard to attract the top players and they will only be able to offer Europa League football if they can overcome Hajduk Split over two legs. Despite this, the Everton boss is hopeful that he can secure at least one of his targets before the window shuts. A striker is a clear priority for the Dutch coach but he is also looking to bring in cover for left-back Leighton Baines.
"We have signed Sandro and Wayne, and we know the development of Dominic [Calvert-Lewin], but we are looking for an extra striker and it is difficult because it needs to be a player of a certain quality or a young player who can improve,” Koeman said. “We know we have the possibility to sign good players but we don’t play Champions League and that sometimes makes decisions very difficult.”
Koeman admits it was an easy decision to pursue Icelandic midfielder Gylfi Sigurdsson after revealing that he had tried to sign the player when in charge of Southampton but finances restricted him.
On this, he said: "We did not have the finance that we have here at Everton. In my opinion, in his position, he is one of the best players in the Premier League. We want more productivity in the team after losing Lukaku and that is exactly what Gylfi brings. We have worked a long time to get this deal done but he is one of the key players we wanted to bring in. Last season apart from Lukaku we did not have one player who scored 10 goals. Now, with Gylfi, Wayne and Sandro, we think that might be different.”
The Everton manager also admits it was difficult to let go of a top professional like Gareth Barry.
“You never want to lose a top professional like Gareth but I could understand his position,” he said. “He knew he would not be appearing every week and he is still the type of player who wants to keep playing. I let him go because I respect him, but I still had to ask myself whether we had enough midfield cover. I think we probably have, with Morgan Schneiderlin, Tom Davies and Muhamed Besic, maybe even Davy Klaassen if necessary, but of course I don’t know how the season will go so I don’t have that answer now. Maybe I will get a headache one day wondering why I let Gareth go.”
Koeman is also open to loan moves as well as permanent transfers but has laughed off the suggestion of bringing Diego Costa on a temporary basis and says he is pleased with the business carried out by his club so far. “We have brought in some good young players in important positions and that is good for the future of the club,” he said. “We are still trying to get more but they have to be of the best quality. We don’t sign players just to get numbers in.”