The newly signed France forward scored his first goal with Barcelona in the first half after Betis had taken an early lead, then took inspiration from Messi to curl in a left-footed shot shortly after halftime.
"I see Messi doing that in practice and I tried to copy him," Griezmann said. To celebrate his second goal, Griezmann went near the Barcelona fans behind the goal, picked up glitter from someone who appeared to be a staff member and threw it up in the air with his arms spread in the style of James' chalk toss routine over the years.
"I like LeBron's ritual and I tried to imitate him," Griezmann said. Griezmann came through for Barcelona as Messi and Luis Suárez watched from the stands because of injuries. Carles Pérez, Jordi Alba and Arturo Vidal also scored for Barcelona. Nabil Fekir and Loren Morón scored for Betis.
Barcelona had lost 1-0 at Athletic Bilbao last weekend for its first opening league defeat in a decade. Messi had already missed that game because of a calf injury, while Suárez got hurt before halftime in Bilbao. Forward Ousmane Dembele also was out injured on Sunday.
Griezmann, who joined from Atlético Madrid for 120 million euros ($133 million) in the offseason, had started at Barcelona with a lackluster performance in the opener. But he took charge on Sunday, scoring his first goal after sliding to a cross from Sergi Roberto in the 41st minute.
Griezmann's second came in the 50th with his well-placed shot that was just out of reach of Betis goalkeeper Dani Martín. "It was an important match for him," Barcelona coach Ernesto Valverde said of Griezmann. "He was fully focused from the start, like all the other players."
Sergio Busquets was superb for Barcelona in midfield but had to be substituted in the 72nd with an apparent injury. Forward Ansu Fati, 16, made his senior-team debut with Barcelona as a second-half substitute, becoming the second youngest to play with the club in the Spanish league.
Atlético Madrid earlier won 1-0 at Leganés to join Sevilla as the only two teams with straight victories to start the league. Real Madrid opened with a win but was held by Valladolid to a 1-1 draw at home on Saturday.
ATLÉTICO KEEPS ROLLING Portuguese teenager João Félix set up Víctor "Vitolo" Machin's second-half goal to keep Atlético with a perfect record. Félix sent a through pass for Vitolo in the 71st minute and the striker found the net from inside the area at Butarque Stadium.
"It was a complicated match, but we leave with the victory," Vitolo said. "We are at the top and we need to keep working to keep our momentum." Leganés, the southern Madrid club which had opened with a home loss to promoted Osasuna, nearly broke the deadlock early in the second half when Jonathan Silva's free kick struck the crossbar at Butarque Stadium.
Atlético was still without striker Diego Costa because of an injury. OTHER RESULTS Norway midfielder Martin Odegaard gave Real Sociedad a 1-0 win at promoted Mallorca, while Alavés drew 0-0 with Espanyol at home.
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