Fabregas was substituted in the 54th minute of Spain's 3-0 win over Nigeria in Fortaleza on Sunday, while Soldado went off six minutes later.
"In view of the test results, neither player's presence has been ruled out for the semi-finals, although their participation will depend on the evolution of the said pains."
Speaking after the Nigeria game, Spain coach Vicente del Bosque had expressed optimism over Fabregas' fitness.
"I guess something happened, he felt a slight pain, and he withdrew to be on the safe side," Del Bosque said.
"Now it's up to the doctors to assess what it is. It doesn't seem to be anything serious, but we're just being cautious."
Italy have several injury concerns of their own ahead of the game. AC Milan team-mates Mario Balotelli (thigh) and Ignazio Abate (dislocated shoulder) have both been ruled out, while there are doubts over midfielders Andrea Pirlo (calf) and Riccardo Montolivo (nausea).