Phoenix skipper Andrew Durante, who said he had rarely experienced such hot weather during his seven years in Wellington, hoped the training exercise would help on Monday.
"It was tough. We were fully-kitted up, tracksuit bottoms, tracksuit tops," he said. "So it wasn't enjoyable; it was difficult. [Merrick] wanted us to train and train under fatigue as we will probably play against in Brisbane."
After a few weeks off due to the Asian Cup, the second-placed Phoenix are ready to return to action and Merrick said nothing had changed around the future of in-demand striker Nathan Burns.
The Phoenix are in negotiations with a Chinese club about selling the A-League's golden boot leader and Merrick said the situation would be cleared up before the end of the transfer window on February 3.
Burns is part of Australia's squad that will play against South Korea in the Asian Cup final in Sydney on Saturday night and will link with the Phoenix shortly after.
"Nathan should be available for our game against Brisbane on Monday night," Merrick said.
Striker Roy Krishna has recovered from a hamstring niggle but the Phoenix could be without defender Manny Muscat after he stepped in a pothole at the Phoenix's Newtown Park training base and rolled his ankle this week.
"It's been very disappointing," Merrick said of the training ground.
Wellington City Council parks, sports and recreation manager Paul Andrews said the recent Colgate Games had put extra pressure on the No 2 field the Phoenix use.
"Newtown Park's a multi-use facility. At this time of the year it's under a fair bit of pressure because we are in the middle of our athletics season," Andrews said.
Meanwhile, the Phoenix confirmed yesterday that veteran defender Ben Sigmund, who has made 154 A-League appearances, has signed a one-year extension with the club that will keep him in Wellington until the end of the 2015-2016 campaign.
