The 23-year-old scored just three times in 20 appearances, including eight starts, in 2013 after a rookie campaign that saw him record seven goals in 21 games.
Mattocks helped Vancouver make the post-season in 2012, but the Whitecaps missed the playoffs this season, leading to Rennie's dismissal last week.
Speaking on the program "Football GPS" on Tuesday, Mattocks criticized Rennie's handling of both himself and the squad.
"When (I was) leading the team, as a rookie, Vancouver made the playoffs," said Mattocks, who started 15 games in 2012 and scored in the Whitecaps' playoff loss to the Los Angeles Galaxy. "My second season, coach put me on the bench (the) majority of the season. (He and I) couldn't agree."
Mattocks also said that teams from England were interested in his services, but that the Whitecaps refused to entertain the idea of selling the forward. The Jamaican international added that the club also turned down a US$1.2-million offer for him from another team in MLS.
"If (I) can do a successful first season and in my second you will try to jeopardize my career, I'm not naive and I'm not going to stay," said Mattocks, who denied he had anything to do with Rennie's firing. "Every other team in MLS wants me."
Whitecaps president Bob Lenarduzzi said on a conference call with reporters Wednesday that he held exit meetings with all of the player last week, including Mattocks, and was taken aback by the comments.
"It's certainly not something that from a club perspective that we would want to have happening," said Lenarduzzi. "That's the kind of criticism really that should take place between the coach and the player or between the club and the player.
"We certainly didn't hear any of that (in the exit meeting), and are disappointed that he's chosen to go that route."
Lenarduzzi said he has yet to speak with Mattocks since the comments, but that he's a player who has required extra attention from coaches and management throughout his young career.
"I think Darren has been prone to ... make comments or sometimes look in games like he's disinterested. We know those are all things that come with Darren, but he's got a special ability so until we decide differently we're going to try to work to bring out the best in him," said Lenarduzzi, before adding: "And at the same time have him appreciate that he can't be doing what he's just done."
Lenarduzzi said the club discussed a potential training stint in England for Mattocks last season, but added that no club offered to buy the second overall draft pick in 2012.
He also said that no MLS team offered $1.2 million for Mattocks, but agreed that he has fielded calls.
"There's interest for a lot of our players from other MLS clubs," said Lenarduzzi. "So I wouldn't suggest that he's alone in that regard."
Mattocks, who made $212,000 this season, found himself way down the Whitecaps' pecking order behind star striker and Golden Boot winner Camilo Sanvezzo, veteran Kenny Miller and 18-year-old phenom Kekuta Manneh because of injuries, inconsistency and international duty.
"Any time you get him kind of in and around the team, he seems to be gone again," Rennie said of Mattocks in October. "That's something that has hurt him a little bit this season."
Notes: As a Generation Adidas player, Mattocks' wages have not counted against Vancouver's salary cap during his first two seasons. That usually changes for a player entering his third year. Lenarduzzi said he expects to hear from MLS on Mattocks' status for 2014 soon. ... Lenarduzzi said the Whitecaps are continuing their search for Rennie's replacement, but declined to disclose how many candidates have been interviewed.