Philippe Coutinho and Ousmane Dembele both scored as Barcelona beat Gimnastic de Tarragona 3-1 in a pre-season friendly.
Lionel Messi wore the captain's armband in his first match since he opted to abandon his plans to leave Barca, although Luis Suarez and Arturo Vidal were left out of the squad as the club is still trying to offload both players.
French winger Dembele rolled the ball into the net to put Barca ahead in the sixth minute in his first appearance since November 2019, having undergone surgery to treat a ruptured hamstring tendon.
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Antoine Griezmann added to Barca's advantage by converting a penalty in the 16th minute although defender Javi Bonilla scored a superb goal from the edge of the area to pull one back for Gimnastic on the half-hour mark.
Club record signing Coutinho got the third goal in the 51st, also from the penalty spot, making his first outing for the team since returning on loan from Bayern Munich, with whom he scored two goals in last month's 8-2 thrashing of Barca in the Champions League quarter-finals.
Koeman, who changed his entire team at halftime by making 11 substitutions, gave debuts to 17-year-old forward Pedri, new signing Francisco Trincao and American forward Konrad de La Fuente, 19, who stepped up from the club's reserve side.
Barca are sitting out the first two weekends of the new La Liga season which began on Saturday due to participating in the Champions League 'Final Eight' tournament last month.
They face Girona next Wednesday in another friendly before making their league bow against Villarreal on Sept. 27.
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