Heading into Saturday's home game against the Los Angeles Galaxy, he has managed only one goal while seeing action in eight MLS games this season. He led the team in scoring with seven goals last season, when he was just a rookie.
"This is the first time in my career that I've gone through such a slump," said Mattocks after practice Friday at Thunderbird Stadium at UBC.
Mattocks, a 22-year-old Jamaican, can't recall going more than two games without a goal during a standout career at the University of Akron before entering MLS. The defending-champion Galaxy (4-2-2) will put his scoring quest to the test, presuming he is playing.
He has struggled to keep his place in the starting lineup, subbing on during three of the past four games.
"Everyone goes through slumps, so I don't want to get myself all up in a knot worried about not scoring or the negative beliefs," said Mattocks. "I have to work for the team and if I work hard for the team, the goals are going to come."
The Whitecaps (2-4-3), last in the Western Conference, are looking for a better effort from themselves after a disappointing 2-0 road loss to Real Salt Lake extended their winless skid to seven games. Coach Martin Rennie, in a rare outburst, and midfielder Nigel Reo-Coker were both extremely critical of the performance.
Rennie implied that some players might not be with the team much longer, while Reo-Coker called the team "soft." But the Caps have been hard to play against at home, where they have gone unbeaten (2-0-2) in four games.
Mattocks said it's critical for the Caps to keep getting good results in order to offset a winless road mark. The Whitecaps are a different team when playing in their stadium with a retractable dome.
"First of all, I would say we play with much more confidence," said Mattocks. "Not that we're not confident on the road. But, I mean, playing at B.C. Place gives us more drive, playing in front of our supporters."
In their last MLS home effort, the Whitecaps overcame a 2-0 deficit to earn a dramatic 2-2 tie against league-leading FC Dallas.
The Whitecaps also beat second-tier FC Edmonton to advance to the Amway Canadian Championship final. With five of the next eight games at home, including MLS and Canadian championship contests, the Whitecaps hope a good result against the Galaxy will lead to a jump up the standings.
"I think we've been playing well at home," said Rennie. "I do think that we need to tighten up a little bit defensively. At times, we've lost concentration when we've, maybe, been attacking and left ourselves a bit too open. So we need to do a better job of (avoiding) that, and I think we need to cut out any individual errors.
"And, I think, when we get chances, we need to be a little bit more clinical."
Which is where Mattocks comes in. Rennie, always coy about his lineup, said there is a good chance the sophomore pro will start.
"I think he's just starting to find his form again," said Rennie. "He had a good game in the Reserves on Tuesday. I think he's been working hard. He's just not had the breaks yet."
Watching Mattocks from the back line, central defender Andy O'Brien figures it's just a matter of time before he breaks out of his scoreless funk. His hard work is a "recipe for success."
O'Brien is also confident that the Whitecaps will get out of their winless malaise before long. He pointed to the Galaxy, who eliminated Vancouver in the first round of the 2012 MLS playoffs, as an example which the Caps can emulate.
The Galaxy struggled last early last season before rallying late in the campaign to win the MLS Cup. But the defender is not certain that the game will serve as a benchmark in terms of helping the Caps see where they stand.
"In North America, it's different to what I've experienced back home (in England)," said O'Brien. "We've been recently watching the ice hockey games here, the playoff games. You have blood and guts and everything.
"In England (in soccer), that's every single week, whereas I think with MLS, you can maybe have a bad start like L.A. did last year, pick up momentum and, when it comes to the business end of the season, really kick on.
"So we've gotta put it into perspective. ... We've still got time to turn it around."
But Rennie and defender Alain Rochat believe the star-studded Galaxy will help the Whitecaps judge their level of play. Reo-Coker, who believes the effects of his and Rennie's comments will become known after the game, offered a slightly different slant.
"It's a great game at the right time," said Reo-Coker. "After the way we performed last week, it's the kind of game we needed, and now we've just gotta step to the plate."
Notes_Vancouver striker Kenny Miller remains out with a hamstring injury. ... L.A. defender Todd Dunivant (leg strain) and striker Robbie Keane (sprained ankle) are expected to return to the Galaxy lineup after being sidelined for the past two games. ... The Galaxy is unbeaten in five all-time league meetings with Vancouver.