Melbourne City unceremoniously bundled Wellington out of the A-League play-offs with a 2-0 win in Sunday's elimination final at Westpac Stadium.
Merrick says the absence of striker Joel Griffiths, who ruptured his anterior cruciate knee ligament three weeks ago against Sydney FC, was keenly felt.
"I don't think we had enough quality options up front," he said.
"It would have been terrific to have a Joel Griffiths, a senior experienced proven goalscorer, under-pressure type player.
"We really missed out on that and I guess that will be our No.1 target for recruiting next year."
City goes on to meet Premiers' Plate winner Melbourne Victory at Etihad Stadium on Friday, while Sydney FC plays Adelaide United on Saturday to decide the other finalist.
Phoenix's late-season goalscoring woes continued, as did a tendency to leak soft goals at the other end of the paddock.
Merrick describes the performance as uncharacteristically uncertain.
"Melbourne City came here with the right attitude. They competed all over the park, they pressed us and stopped our midfield."
Phoenix striker Nathan Burns, second on the A-League golden boot standings with 13 goals for the season, came under particularly intense scrutiny.
"Nathan is our most experienced striker, and they always had two men on him. He never got his shots off on target, and if he did they weren't great shots," Merrick said.
"All year we've been about keeping the ball, about going forward, and it was just all very tentative.
"We took a step backwards today."