David Villa's form is crucial to Atletico Madrid's La Liga title chances - and his World Cup place, Gaizka Mendieta told Revista.
The striker netted his 12th and 13th goals of the season in quick succession at Celta Vigo to seal three points for his side and capitalise on Barcelona's slip-up against Valladolid.
Crucially, the Spain international stepped up to the plate in the absence of Atletico's top scorer Diego Costa, who was sidelined through injury.
Mendieta says the former Barcelona man will have to continue to find the net between now and the end of the season if Atletico are going to maintain their title challenge and close on leaders Real Madrid.
But the former Valencia midfielder says Villa is also fighting for a World Cup place, after missing out on Spain's squad for their recent friendly with Italy.
"It's very important for him personally and for the club," said Mendieta. "With Costa not being on the pitch Villa had to take responsibility and score the goals - and he did.
"You can't rely on only one player like Costa, who has only scored two goals in 2014. That shows what Atletico need from the team and especially someone like Villa.
"For him personally as well, it's important for the national team. He's not been called up for the last one but Costa is there.
"How many strikers is [Spain coach] Vicente del Bosque going to take [to Brazil]? It's down to every Spanish striker to prove they are capable of being in his squad."
Mendieta says Atletico's win at Celta Vigo also sent a message to their title rivals that they shouldn't be written off yet.
The club are currently three points adrift of neighbours Real - and Guillem Balague says they will need Villa's experience during the final weeks of the season.
"Villa is important because he is perhaps the only guy there used to fighting for trophies, trying to win every game - and that mentality you need in that kind of team," he said.
"Villa was very frustrated because he'd scored in three consecutive games before he got injured but he's come back and he's strong."