Luis Suarez returns to Camp Nou on Saturday in an Atletico Madrid shirt for the first time since leaving Barcelona last summer.
Suarez missed the first meeting between the two teams in November after contracting coronavirus while on international duty with Uruguay.
Ronald Koeman was tasked with telling Suarez he didn't have a future at the club last summer, although the decision was effectively made for him.
Asked about Suarez's return this weekend, the Dutch coach said: "It will probably be strange for Suarez and for our players, he was here for many years.
"But we are professionals. Everyone will give there all to win the game. There's no need to go round in circles on this. We have to focus on him but also on Atletico's other players."
Suarez has scored 19 goals in the league since joining Atletico last summer to help Diego Simeone's side sit top of the table with just four games to go.
If Atletico beat Barça, they will be three wins from the title. If Barça win, they will leapfrog them in the table, but a Barça win or draw would leave the title in Real Madrid's hands.
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