Ronald Koeman believes Everton’s flurry of activity in the transfer market proves he made the right decision to leave Southampton.

Koeman has shelled out around £130 million this summer bringing in the likes of Gylfi Sigurdsson, Jordan Pickford, Michael Keane and Wayne Rooney, as the Toffees bid to force their way into Premier League’s top four.

Hii decision to quit Southampton in 2016 was questioned by many people after he had guided the club to sixth in the table, but Koeman recognised the potential at Goodison Park.

With Everton co-owner Farhad Moshiri eager to establish Everton as a top club, Koeman says the arrival of players like Sigurdsson vindicates his decision to leave St Mary’s.

“Sigurdsson has added value to the team, with his experience and with efficiency in his game,” he told De Telegraaf.

“It doesn’t mean we’re done already. There must be a good deal and that’s a complete search. I’m sure, too, because the club shows its ambitions in the transfer market. I think everyone now understands why I chose Everton last year.”

With Koeman expected to add another striker to his squad before the transfer window closes, talkSPORT pundit David Preece believes the Dutchman should pull out all the stops to sign Chelsea’s Diego Costa.

The 28-year-old has refused to return to Chelsea after falling out with manager Antonio Conte and Preece thinks he’d be a perfect fit for Everton.

“Costa is still back in Brazil and Atletico Madrid are the only club he wants to go to, but they can’t buy him,” he said.

“Koeman was asked the question (whether he’d sign him) and he said he wouldn’t be averse to it.

“They’ve got the money for it, there’s no doubt about that. They’ve got plenty in the bank.

“If they could get him on loan for a year that would be an absolute masterstroke.

“He’s got to come to a point where he realises the situation at Atletico Madrid won’t just resolve itself.

“He can’t sit out in Brazil for a full year. It wouldn’t do him any good, because by the time he went to Madrid he’d be out of shape and he won’t be of any use for them.

“It’s the one thing Everton are missing now. All the signings they’ve made are going to keep them where they are.

“They may try and break into the top six and this signing would be a real show of intent from them.

“They’ve done the defensive part of it and now they need someone who will get them goals in tight games and who will make a difference.

“Diego Costa could do that. It might be a long shot for them but financially they could come up with a package no problem.”