Chelsea manager Jose Mourinho is yet to decide whether to risk striker Diego Costa for the Barclays Premier League leaders' clash with Stoke on Saturday.
Costa suffered a recurrence of his hamstring problem in last month's 3-2 win at Hull and withdrew from international duty with Spain.
Chelsea's top scorer will be in the squad for the Stamford Bridge fixture, but may not start.
Mourinho said: "Diego trained (on Thursday and Friday) with the group. He's not injured. I don't know if I start with him or not.
"We did all the tests and the scans to confirm two days ago scientifically the situation and in this moment the muscle is fine.
"But football is more than that. You need confidence. You don't need to break your intensity. That's our doubt. Let's see next 24 hours."
Asked the long-term solution to Costa's recurring problems, Mourinho insisted an operation would be undertaken only if there was no alternative.
Mourinho added: "I don't believe we will ever go in the surgery direction.
"(The solution) is to work the way he does all the season in prevention, in making the muscle stronger and at the same time elastic and flexible. Recover well – not a big accumulation of fatigue – and this is what we can do."
Chelsea have one game a week for the season run-in, apart from when they meet Leicester in midweek later this month in a match rearranged due to the Capital One Cup final.
"It's better," Mourinho said. "That's why this weekend is the weekend where we are a bit short of time.
"With a normal week of work, playing one match every weekend, normally he should be fine."
Chelsea are six points clear of second-placed Manchester City with that game in hand, but Mourinho believes the title race is open and even fourth-placed Manchester United, who are eight points behind, are in contention.
"With eight matches to go it is a difficult gap from the first to fifth, but the points difference between second, third and fourth make me feel that they are there," Mourinho added.
"In the last matches they (United) become consistent in results and also the quality of their performances.
"We need six victories and one draw in nine matches, so a good situation for us, a situation that all the other clubs would like, but it's pure mathematics."
In winning the title in 2005 and 2006, Mourinho predicted when and where Chelsea would lift the trophy.
It is "too early" to make such bold claims this time.
He added: "If we are champions in the last match, I'm more than happy with that.
"I'm not thinking about how or when. I'm just thinking that we need to win six matches and draw one.
"Every victory we have now is one victory less that we need and is one less occasion for our opponents to reach us.
"I don't care if it's in the hotel, or away or at home. I just want to win it.
"Many occasions in the Premier League the clubs get the trophy in their last match at home.
"Our last match of the season is at home so if we win the title we get the trophy at our house, but I don't care even if somebody loses the trophy and we don't get the trophy. I'm happy with that.
"I just want to win it."
Captain John Terry would lift the trophy if Chelsea are successful, having signed a one-year contract extension during the international break.
"I knew it (would happen)," Mourinho said.
"We all found the period without football as a good moment to sign it, to make it public and everybody knows two months before the end of the season that John is staying one more season."
Mourinho expects Stoke to be a challenging opponent and was straining his voice when speaking to the media after tactical sessions this week.
He said: "I think it was (Thursday's) training session. It was a good one, an intense one.
"I was also an important part of the training session. They need their legs, I need my voice. I lost my voice.
"Maybe because my voice was quiet for the last couple of weeks, I lost it."
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