The Navy Blues capitulated in the second half after trailing the Portuguese side 1-0 at the interval, in a performance which followed up a 10-0 thrashing from German giants Bayern Munich in their opener.
The result means Auckland City have no chance of qualifying for the knockout stage, and will only be playing for pride in their final match against Argentina side Boca Juniors on Wednesday morning (NZ time).
Saturday’s game featured a delay of more than two hours at halftime due to a heavy storm, at which stage Auckland trailed 1-0.
They initially defended more stubbornly than they did in the the rout against Bayern Munich, led by a series of quality saves by goalkeeper Nathan Garrow.
The dam burst on the stroke of halftime when former Manchester United star Angel di Maria converted from the penalty spot.
The lengthy halftime delay may have affected semi-professional Auckland's focus as Benfica's mountain of attacking raids started to find cracks in the defence.
Vangelis Pavlidis and Renato Sanches added goals soon after the break, before Leandro Barreiro scored in the 76th and 78th minutes and Di Maria converted a second goal from the spot to round out the scoring.
In other games on Saturday, Harry Kane opened the scoring for Bayern Munich in their 2-1 win over Boca Juniors, Chelsea suffered a 3-1 loss to Flamengo, and Esperance de Tunis beat LA FC 1-0.
Yesterday, Valentin Carboni scored in the second minute of second-half stoppage time to complete Inter Milan's rally to a 2-1 victory over Urawa Red Diamonds in Seattle.
Carboni's strike rescued all three points for Inter, 14 minutes after Lautaro Martinez's brilliant, volleyed 78th-minute equaliser from a corner kick.
Against the run of play, Ryoma Watanabe had put Red Diamonds in front in the 11th minute.
Takuro Kaneko created the opportunity with a wonderful slaloming run from the right into the penalty area that split two Inter defenders, before dragging a cross back toward the penalty spot.
Watanabe met it with a first-time, side-footed shot that deflected off another defender, wrong-footing goalkeeper Yann Sommer on its way into the bottom right corner.
Jobe Bellingham, brother of England and Real Madrid star Jude Bellingham, scored for German club Borussia Dortmund in their 4-3 win over gutsy South African side Mamelodi Sundowns, and Fluminense beat Ulsan Hyundai 4-2.
In the final game of the weekend, Argentina’s River Plate and Mexico’s Monterrey battled to a nil-all draw at the Rose Bowl in Pasadena.
Despite dominating the match with 18 shots to Monterrey’s three, all River Plate had to show for its efforts was a red card for midfielder Kevin Castano, who received his marching orders in stoppage time after a second yellow and will now miss his side’s crucial final group match against Inter on Thursday . — RNZ/Reuters/Field Level Media
