Chelsea may have to make an emergency movement for a defender after a shock injury to Levi Colwill this summer.
The Blues defender, who came forward as a key figure for Enzo Maresca last season, took a mystery problem in the first training session of Blues from the preseason.
Chelsea returned to the training on Monday after their Triumph Triumph last month, but was immediately returned to Earth.
Colwill was sent on Tuesday evening for a scan with figures in the club that was involved, it could be an important knock.
Maresca hinted that Chelsea, depending on the results of the scan, may have to sign a replacement this summer.
The Italian said: “We had a problem with Levi Colwill for the past two days, that we do not know how long he will be gone.
“We will see, hopefully not too long, but it is certainly a problem for us. We have to wait, we don't know yet.
“It was in the first session on Monday, just in the last minutes of the session. He felt something and, as I said, we have to wait and then we see.”
Asked if they will sign a replacement, Maresca added: “It depends on it. We have to wait and then we see.
“But, as I said, we know each other from last year and you know how important Levi has been.
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“I spoke to him yesterday and I told him that if we achieve what we achieved last year, this is also because of him – and he was a main player for us.”
Graduated Academy graduate Colwill emerged as a leader in the past term of Maresca, as a result of which 43 performances appeared in all competitions.
Although they may now have to add another defender, spending remains an important part of the summer of Chelsea.
Maresca has almost confirmed the open secret that striker Nicolas Jackson can leave when the right offer arrives.
Chelsea appreciates the Senegal International at £ 80 million, with interest from Newcastle.
The blues boss said: “Nico is fine. He is okay.
“When the transfer window is open, unfortunately or happy, everything can happen. This is also about Nico's situation.
“At the moment we also had two strikers, both in the US, Joao Pedro and Liam Delap. So we will see what happens.”