After watching the Mets’ recent call-ups in action manager Terry Collins probably has a good idea why tigers eat their young. “You think some of these guys will grab the opportunity that’s in front of them because of the injury issues on our club and say ‘Here’s my chance to show I’m a major league player’ ” Collins said. “And we’re not seeing it.” Lucas Duda Travis d’Arnaud Matt den Dekker Zach Lutz and Ruben Tejada are among the arrivals over the last month who have struggled offensively. On Thursday the Mets scored two runs or fewer for the fourth time in five games allowing the Nationals to complete a four-game Citi Field sweep with a 7-2 victory. The loss was the Mets’ ninth in 11 games overall. Collins later admitted he addressed his team earlier in the week about maintaining a proper mindset. He indicated he may need to speak again to his team before the Mets open a four-game series against the Marlins beginning Friday at Citi Field. The manager said it’s essential his young players understand self-pity is unacceptable. “I will not stand for that” Collins said. “Not in this clubhouse not in this league you don’t feel sorry for yourself. Nobody feels sorry for you in the game. Our guys in that room because a lot of them are young they better learn that lesson real fast because if they’re going to play here they better know how to bounce back.” The Mets’ lack of power was underscored during a four-game series in which the Nationals out-homered them 13-0. The last homer by a Mets player came in Cleveland on Sunday when Justin Turner cleared the fence.