"It was down to our own mistakes in the first 30 minutes or so that set them up for the win really. We gave away possession too often and made silly kicks and we really expect more of ourselves than that," he said.
There were plenty of positives to take from the match but overall the feeling on the way home was one of disappointment over a lost opportunity. Williams said there were no regrets over taking the points when on offer and in the end they were just one penalty kick away from taking the lead late in the game.
"Our thinking was that we should put pressure on them by piling up the points and it did work because we were just two points behind them before we let them back into the game," he said.
Northland were clearly better in the set-piece with Williams snatching a number of line-out steals to get them valuable possession but Waikato were more clinical in attack outscoring Northland three tries to one.
The first went to flanker Rory Grice in the 16th minute but Northland were soon back on attack. Unsurprisingly, Rene Ranger was at the heart of much of Northland's positive play, with Waikato double teaming the Taniwha skipper on defence for much of the match.
Ranger was involved again as Waikato scored their second. His poor clearing kick went straight to Grice and, after he began a counter-attack, Joe Webber darted down the right wing to cross untouched.
After an opening half of missed opportunities, Northland began the second spell determined to make amends. It took only one minute for Sonatane Takulua to go under the posts, after Jake Paringatai came off the back of a scrum and put the halfback through a gaping hole.
With Northland's Ben Seymour on song with the boot, the deficit was soon down to two as he traded penalties with Trent Renata as the excitement grew in the second spell. Both teams were guilty of blowing opportunities to apply real pressure as errors increased as the rain intensified.
But Toby Smith finally eased his side's nerves, burrowing over in the corner to clinch the game with less than 10 minutes left. A length of the field consolation try to Mateo Malupo was disallowed by the television match officials for a forward pass, leaving Northland without a bonus point for their effort.
Waikato 31 (Grice, Webber, Smith tries; Renata 4 pens, 2 cons) Northland 22 (Takulua try; Seymour 5 pens, con) HT: 18-9