Otago United coach Terry Phelan said he was embarrassed about his side's display.
"It was a joke. Two goals in 2min . . . we must have given the ball away straight from our kick-off,' he said.
"We were second to the ball, never won any knock-downs, there was poor decision-making, and they jumped into tackles selling themselves.
"No need for Robbie Deeley to tackle even, but he dived in - and we were reduced to 10 men," Phelan said.
"There will be changes next week. They didn't look prepared mentally. They might get away with it in the winter league, but not at this level."
Phelan said the best players for Otago were the three substitutes who went on with 20min to go: Mike Smith, Tom Connor and Sean Brand, who all did their jobs.
Otago initially made a bright start, and in the 9th min, Tom Jackson carved past defender Nathan Strom before chopping back and hitting a low shot past new Waikato keeper Greg Walters, a 1.89m recent signing from the professional Carolina Railhawks USL team.
Aaron Burgess and David Dugdale created some chances, but the Waikato defence, well led by Graham Pearce, got over early jitters.
Two possible penalty decisions at either end had referee Michael Hester yellow-card Tristan Prattley perilously close to the edge of his penalty area, then Otago was denied a similar good shout for a spot kick in Waikato's box.
In the 34th min, Stu Hogg jumped above Otago defenders to powerfully head the equaliser, then from the kick-off, another strong run down the left by Hogg produced a cut-back for Nik Keown Robson to feint round keeper Liam Little and put Waikato in front 2-1.
Former University of Otago player Paul Stewart was also yellow-carded, but referee Hester went for the big one when he red-carded Deeley for a lunging tackle at yet another former Otago player, Joe Simpkins, in the 43rd min.
Otago had a mountain to climb in the heat butbattled on, and when Burgess and Jackson were replaced by the Roslyn pair of Connor and Brand, the visiting side looked capable of equalising at least.
Phelan urged his troops forward, putting on Mike Smith for Barry Gardiner and generating pressure on Waikato which soaked it up.
Waikato's Strom turned the tables on Otago with some long throws that had the exhausted Otago players struggling, as the home side used its extra-man advantage.
Tim Horner went down with a leg injury scare, but battled on in defence.
Just on full time, there was a rash tackle from Rhys Henderson on Hogg, and after referee Hester flashed another red card, this time at Henderson, Hogg tucked away the penalty giving Waikato its first back-to-back win of the season.
• Bottom-placed Canterbury opened its account with a surprise 1-all draw with top team Waitakere when Gareth Turnbull headed the equaliser after a goalkeeping error, NZPA reported.
Manawatu remains top on nine points despite an injury time 1-2 loss to visiting Hawkes Bay, while reigning champion Waitakere United moved to second on seven points, with a game in hand, despite a 1-1 draw at home to bottom-placed Canterbury United.
Auckland City lost 1-2 to Wellington in the capital, which left both sides on six points and tied with Waikato and Hawkes Bay.
