Atletico Madrid midfielder Tiago is to undergo further tests to ascertain the severity of a hamstring injury sustained against PSV on Tuesday.
Tiago replaced Nicolas Gaitan in the 61st minute of the Champions League clash, which the LaLiga side won 1-0 in Eindhoven.
However, Atleti confirmed on their official website that Tiago hurt his right hamstring during the game and the 35-year-old is waiting to learn the extent of the damage.
"Tiago Mendes suffered a hamstring injury in the back of the right thigh, according to a first examination made after the match played by Atletico de Madrid and PSV Eindhoven," read a club statement.
"In the next 24-48 hours, the Portuguese midfielder will undergo imaging tests that will determine the extent of his injury."
Atletico Madrid host Sporting Gijon at the Vicente Calderon on Saturday, with Diego Simeone's men having taken five points from their opening three LaLiga matches.