"The boys - I think it's got something to do with the travel.
"The last 17 rounds, we've been in New Zealand six times, and only four at Westpac, so we don't seem to have a home advantage anymore.
"It's a fairly horrendous draw and the boys didn't cope with the heat. They weren't up for it."
Merrick took no solace from the fact they have five games at Westpac Stadium in the final seven matches.
Second-game striker Hamish Watson scored his first and second goals in the A-League for Phoenix to give them a 2-1 lead at half-time.
But the 22-year-old injury replacement signing was then sent off for a second yellow card in the 71st minute after kicking the ball away at a Jets free kick.
A 27th-minute own goal from Andrew Durante and a double to former Denmark international Morten Nordstrand in the 53rd and 73rd minutes gave Newcastle the win. Merrick said Watson's day summed up Wellington's season.
"He's just immature really," he said. "He hasn't really played at this level very much. We finally bring him in, he scores two goals, then gets himself sent off. And we haven't had a striker all year virtually, so it's not been a good year.
"A very disappointing year. A disappointing draw. I won't even mention the refereeing. He's fulltime as well? I better not say too much. I'll get another fine.'
-AAP