Luis Suarez partnered Diego Costa for the first time and scored as Atletico Madrid beat struggling Celta Vigo 2-0 win in La Liga on Saturday.
But the Suarez-Costa combination came to an early end as Costa was forced off injured in the second half.
Sitting in the stands, Costa was seen with his face in his hands and he was also hobbling after the final whistle.
He is now likely to miss Atletico’s Champions League opener away at Bayern Munich on Wednesday.
Atletico climb to fourth, two points behind early leaders Real Madrid and one ahead of Barcelona, after the win. Celta, meanwhile, have managed only one win from their first six games and sit 13th.
This was a much-needed victory for Atletico after back-to-back goalless draws had dampened enthusiasm following their 6-1 opening win against Granada.
Suarez made his debut that day, coming off the bench to score twice when Granada were already down and out, but his early strike shaped this game against Celta, until Yannick Carrasco headed in a second in injury-time.
Diego Simeone had kept Suarez and Costa apart by using one to substitute the other in each of Atletico’s first three matches but he paired them together from the start at Balaidos, with Joao Felix on the bench.
Costa predicted last month they would be handful together, saying “it will be good, one bites, the other one kicks.”
There were flickers of chemistry, with Suarez missing a chance for a second from the Costa pass that caused him to feel pain in his lower leg.
“He’s important because of his career and what he has done at Atleti,” said Suarez. “We try to adapt to each other despite never having played together before.”
Felix also impressed when he came on and will provide a more creative, if less combative, foil for Suarez in Costa’s absence.
After replacing the injured Costa after half-time, it was Felix’s curling shot that hit the bar, allowing Carrasco to nod in the rebound.
Suarez had earlier put Atletico in front in the sixth minute, sweeping in after 20-year-old left-back Manu Sanchez picked him out with a clever pull-back.
There was also a debut for Lucas Torreira, the Uruguayan signed on loan from Arsenal, who was energetic and tidy in central midfield, despite feeling some cramp late on.