Fabregas played the whole of Chelsea's 2-1 Premier League win over Liverpool on Saturday but Blues boss Jose Mourinho admitted afterwards he had taken a "gamble" with the 27-year-old's hamstring problem.
Mourinho also said that Fabregas could link up with Spain ahead of their upcoming matches against Belarus and Germany, but added that he "would be back" as he was not fit
Fabregas is now set to undergo tests with his national team on Monday to determine his availability
Spain team doctor Oscar Celada told Radio Marca: "We will assess him in the coming hours to see if he can form part of the squad.
"We know Cesc, I've known him since he was 16 years old, I know his professionalism and commitment to the national team, but we are still waiting to assess him."
Spain coach Vicente del Bosque added on the national team's official website: "The most prudent thing is that he sees the Spanish national team medical staff
It's not a lack of confidence in the medical staff at his club, but after playing 95 minutes this weekend we would like to see him and examine him."
Fabregas has shone since joining Chelsea from Barcelona this summer, and has forged an impressive partnership with another new boy in Diego Costa.
Costa is also an international colleague of Fabregas', although the Brazil-born striker is not part of the current Spain squad after Del Bosque decided to rest him.
Costa, who scored the winning goal against Liverpool before being replaced late on by Didier Drogba, has been hampered by a hamstring problem that he had at previous club Atletico Madrid.
Celada said of Costa: "We have regular contact with the medical services of all the teams
We were aware that he has some discomfort, something that allows him to train sometimes but not others.
"We spoke with the player and with Chelsea and we took a decision which was for the best, to rest for these two weeks
Then his team decided that he was able to play (against Liverpool) and there's no problem.
"We did it because medically it is good for the player and if that results in the good of his club then we are happy."
Del Bosque echoed those comments, saying: "We thought that calling him up for the two games would be counter-productive for his health and thinking of the player we preferred that he took a break
There's nothing more."
Spain host Belarus next Saturday in a European Championship qualifier before then facing the side which this summer took their world crown, Germany, in a friendly on November 18.
Source : PA