Gameiro scored the winner from the penalty spot in the 34th minute after forward Saul Niguez had his jersey pulled inside the area.
Atletico Madrid took advantage of Barcelona's stumble to keep alive its title hopes in the Spanish league.
Kevin Gameiro converted a first-half penalty kick as Atletico defeated Deportivo La Coruna 1-0 on Sunday to move within nine points of leader Barcelona with eight matches remaining.
Barcelona lost points in a 2-2 draw at Sevilla on Saturday when it needed two very late goals by Luis Suarez and Lionel Messi to remain the league's only unbeaten team this season.
"We will keep doing our part and then we will see what happens," Atletico coach Diego Simeone said.
Gameiro scored the winner from the penalty spot in the 34th minute after forward Saul Niguez had his jersey pulled inside the area.
Deportivo La Coruna stayed winless in eight matches under coach Clarence Seedorf. The team is second-to-last in the standings and hasn't won in 15 matches.
"I'm proud of how our team played," Seedorf said. "We played a great match against a great opponent. We need to start scoring goals to be able to win matches."
Deportivo has lost five of its eight games with the former Dutch midfielder, having scored only two goals and conceded 10.
Atletico's next league game is at third-place Real Madrid on Sunday.
VALENCIA THRIVES
Valencia defeated Leganes 1-0 to extend its impressive run and stay close to Real Madrid in the fight for third place.
Striker Rodrigo scored a second-half winner to give Valencia its seventh win in eight matches. It's one point behind Madrid, which on Saturday won 3-0 at Las Palmas. Valencia is five points behind second-place Atletico Madrid.
Valencia opened a comfortable 15-point lead over fifth-place Villarreal — 62 to 47 — practically guaranteeing the last Champions League spot for next season with eight matches left.
"We know we are very close to this fourth spot, but it's not secured yet," Valencia coach Marcelino Garcia Toral said. "We should be able to earn it, but this is football and anything can happen."
Valencia is unbeaten in its last eight matches, with the only setback a 1-1 draw at Athletic Bilbao four rounds ago. Its recent run follows a streak of six consecutive losses in all competitions.
Leganes is on 36 points with Athletic Bilbao and Espanyol.
MALAGA WINS AGAIN
Last-place Malaga ended its 14-match winless streak by defeating fifth-place Villarreal, thanks to a first-half penalty kick converted by midfielder Chory Castro.
Malaga, which had lost 11 of its last 14 matches, is 11 points behind Levante, the first team outside the relegation zone.
Villarreal, which was coming off a win over second-place Atletico Madrid, is one point ahead of Sevilla and three in front of seventh-place Girona, the last team securing a Europa League spot next season.
DERBY DRAW
Real Sociedad could not manage more than a 0-0 draw at Basque Country rival Eibar in the debut of coach Imanol Alguacil.
Sociedad, which has won only one of its last seven matches, remains near the bottom of the table in 15th place, while Eibar is 10th.
LACKLUSTER DRAW
Alaves halted a three-match losing streak by holding Espanyol to a 0-0 draw at RCDE Stadium in Barcelona.
The result kept Alaves in 16th place, 11 points from the relegation zone.
Espanyol is four points in front of Alaves.
