"We've got to tighten up defensively," he said. "We've been conceding goals and giving away cheap and easy goals. You can't do it at this level. You're going to get punished."
The Whitecaps (4-5-4) will try to kick the habit as they host the New England Revolution on Saturday.
The Seattle Sounders overcame a 2-1 deficit to beat the Whitecaps 3-2 last weekend. The loss was compounded by a hamstring injury to top central defender Andy O'Brien, who will miss the game against the Revs (5-4-5).
The Whitecaps were leading in Seattle when O'Brien left, but could not maintain the advantage with a makeshift back line.
However, the Whitecaps were squandering leads in the second half even with him in the lineup. Vancouver had to settle for draws in a league game against Portland and the second leg of the Canadian championship final against the Montreal Impact.
Both ties occurred on the home turf at B.C. Place stadium — a cause for concern as the Whitecaps prepare to meet a New England team that is unbeaten in six games, including U.S. Open Cup play.
The Revs have scored nine goals in their past two games, and allowed a league-low nine goals in MLS contests.
Injuries on Vancouver's back line threaten to produce more second-half breakdowns.
Carlyle Mitchell, recalled from lower-tier FC Edmonton, will replace O'Brien and Johnny Leveron will continue to play the other centre back spot in place of captain Jay DeMerit, who has missed most of the season with a ruptured Achilles tendon.
Reo-Coker, a former English Premier League star who joined the team in pre-season, said the Caps have to mature quickly.
"It's a learning curve," he said. "Some teams go through these little periods. It's about learning from the mistakes.
"We've got quite a few new players here (from last season.) We've got some young players here. But we've got enough experienced players to make sure those mistakes don't happen."
He called on players to take on more responsibility and communicate better on the pitch as the Whitecaps attempt to finish in the top five in the Western Conference and earn a playoff berth.
Coach Martin Rennie is concerned that the club is giving up goals in the second half, but noted it is not surrendering late markers like it did during a stretch last season. Generally, he likes the way the team has been finishing games.
The Whitecaps have also displayed more finish around the net lately, producing eight goals in their past four games, including league and Canadian championship play. If not for some close misses, the Caps could have had several more goals.
Rennie hopes the trio of Brazilian Camilo, Scottish international Kenny Miller and Russell Teibert of Niagara Falls, Ont., will continue to develop the chemistry that they have displayed lately.
After struggling to maintain a lineup spot earlier in the season, Camilo now leads the team in scoring. He accounted for all of Vancouver's scoring in Seattle and has four goals and an assist in the past four games, including Canadian championship play.
Miller, who has missed most of the season with a hamstring injury, has three goals in the five league games in which he has played. Teibert has been on a tear since scoring his first two MLS goals in a 3-1 win over the Los Angeles Galaxy on May 11.
The Canadian midfielder, used in a much more attacking role of late, has three assists in the past two games. Factoring in his two goals, he has generated five points in the last four contests.
"It's an exciting combination and it's only just starting to take root," said Rennie of the trio.
Miller said he, Camilo and Teibert are "a work in progress" and can only improve over time. They can also play a role defensively by pressuring the opposition defenders and giving them less time to see the field and move the ball.
But the whole team needs to get "in sync." Once the necessary cohesion is achieved, it will become "an art."
In the meantime, Reo-Coker is calling on a young players like Mitchell to help make up for O'Brien's absence and limit opposition scoring chances.
"The responsibility is on them to show that they want to be here — and they want to play," said Reo-Coker.
Notes: Striker Darren Mattocks has rejoined the Whitecaps following international duty with the Jamaican national team. He will be in the squad Saturday, but appears unlikely to start. ... Leveron has been added to the Honduran national team roster for a World Cup qualifier against the U.S. in Salt Lake City on Tuesday. He will return in time for Wednesday's home game against Chivas USA.