COBHAM, United Kingdom (AFP) - Chelsea boss Jose Mourinho has launched a thinly-veiled attack on Roberto Martinez in response to the Everton manager's accusations that John Terry has "illegally" tapped up John Stones.

Mourinho has made Everton defender Stones one of his main transfer targets, but has so far been unable to persuade Martinez to sell the 21-year-old England international.

Terry highlighted Chelsea's interest in the highly-rated youngster when he spoke of how the Premier League champions are "looking to the likes of John Stones for the future, so the club will continue to grow and do well", prompting an angry response from Martinez, who said what the Chelsea captain did was "wrong" and against "rules and regulations".

But on Friday, Mourinho dismissed those complaints in a clear dig at Martinez, saying: "My feeling is just one and I'm not speaking about Everton or Stones. I'm just speaking in general.

"If I could, I would speak with you (the media) once in a month. And there are other people in football who if they could they would have a press conference every day. And I don't want to say anything else."

Mourinho also claimed he doesn't know if Diego Costa will be fit to start for Chelsea in their opening Premier League match against Swansea City on Saturday, but does not feel the Spain star's ongoing hamstring problem will force him to sign another forward.

The Portuguese also stated that he would prefer a "top player" like Costa who is only occasionally fit, rather than someone always available who does not have the same impact.

Costa missed last week's Community Shield defeat to Arsenal with the injury that plagued much of his 2014-15 campaign and, speaking before Chelsea trained on Friday, Mourinho said he was waiting to survey the former Atletico Madrid player's condition.

"I think he's going to train with the team. His reaction after that and his decision to be confident to play is another story," Mourinho said.

PERFECT NUMBER

Asked whether he felt he needed to buy, Mourinho said no, and insisted Costa does the work of "1.5" forwards when he plays.

"I have (Loic) Remy and (Radamel) Falcao. I go with Remy and Falcao like I did in other matches (if Costa isn't fit), like I did last season so many times with Remy and (Didier) Drogba," he said.

"But obviously he's a top striker. Not just for the goals he scores, but the football he produces.

"I cannot say I don't need him, but I don't like to speak about injured players.

"We brought Falcao because we know that we need three, we need protection to this situation. Three is the perfect number and we have three."

When it was joked that Costa's injuries mean he only has 2.5 strikers, Mourinho shot back: "The half when he plays is one and a half, so compensates, because he's a fantastic player.

"There is nobody to blame and that is very important. I can't blame the player, because the player works hard."

Mourinho did again stress that Chelsea would seek to sign a left-back.

"It's a basic thing. We have only (Cesar) Azpilicueta. We need a left-back, the board knows that, we all know that," he said.

"My feeling is that we are going to have one. But obviously there is not only one left-back in the football world.

"There are more, there are different options and we'll decide when it's possible to decide." Mourinho meanwhile said he is not concerned by Chelsea's failure to win a single 90-minute game in pre-season.

"No problem about four or five matches without a victory in 90 minutes," he said. "If you ask me if I want to play better, defend better, score more, yes I want to do that.

"We have more than a week to work. No problem."