Portuguese champions Benfica needed a stoppage-time strike from summer signing Haris Seferovic to secure a 1-0 win away to Chaves in their second outing of the new campaign on Monday.
The Swiss international forward turned in a Rafa Silva assist in the 92nd minute to make it two wins from two outings for Rui Vitoria's side.
Seferovic, a summer signing from Eintracht Frankfurt, had also scored in the 3-1 home victory over Braga with which Benfica started their campaign last weekend.
Prior to his intervention, the closest Benfica had come to scoring on their trip to Portugal's far north came when Brazilian forward Jonas struck the post just after half-time.
The Lisbon club join their traditional rivals Porto and Sporting on maximum points after two matches, as well as the modest Rio Ave.
Last season's runners-up Porto have enjoyed a perfect start to this campaign under new coach Sergio Conceicao. They made it two wins from two on Sunday as Vincent Aboubakar's goal secured a 1-0 success at Tondela.
Third last season, Sporting have also won their opening two matches although they needed a late penalty from Dutch striker Bas Dost to see off Vitoria Setubal 1-0 in Lisbon on Friday.
Portugal midfielder William Carvalho, said to be on the brink of a £30 million (33 million euros, $39 million) move to Premier League club West Ham United, did not play in that game, apparently due to injury.
Sporting coach Jorge Jesus said that Carvalho would also play no part in Sporting's Champions League play-off first leg at home to FCSB of Romania on Tuesday, amid talk that the deal is nearing completion.
The other side with maximum points are Rio Ave, 2-1 victors away to Boavista on Saturday.