At Ajax Sarpong played alongside Phoenix midielder Roly Bonevacia and Merrick said that link had been beneficial.
"It is always good when a regular member of your team is able to give you information on the person you are trying to sign," Merrick said.
"You are able to get an insight into the lad's character and what Roly had to say was excellent.
"On the football side Jeffery has pace and is a good one on one dribbler.
"Technically and tactically he is a good player who played 10 times for the Dutch under-21 side.
"He has just turned 27 so is at a good age and can get even better."
Sarpong said it wasn't an easy decision to move to the other side of the world but now that he had made it he was looking forward to living in Wellington with wife Stacey and 22-month-old daughter Zoe.
"I had a few options in Europe from good teams in good leagues," Sarpong said.
"I had to think hard about what was best for me at this stage in my career.
"It wasn't easy but the way the manager (Merrick) spoke swayed me.
"He knows how I play and knows areas I can improve in.
"Knowing that he wants to make me a better player was a key."
Sarpong has often been used as a wide player and says that while he has plenty of assists to his name he wants to score more goals.
"It will be a challenge for me but I have a good feeling about the manager," he said.
"I don't know much about the A-League apart from what Roly has told me.
"I have had a lot of conversations with Roly because we are good friends and he told me about the league and what the Phoenix club was like."
During his time at Ajax Sarpong played alongside Luis Suarez, who he described as "some player", but soon it will be the likes of Michael McGlinchey, Alex Rodriguez and Bonevacia setting up goal-scoring chances for him rather than the mercurial Uruguayan.