Saturday's 2-1 defeat to Watford has left Steve McClaren's men languishing in the bottom three of the Premier League after 23 matches.
Newcastle have already conceded 41 league goals and have been near the foot of the table for most of the season.
"Maybe we are too nice. It is true that we need to win more tackles. If you look at all the 50-50's at the moment, maybe we are losing more than the opposite side and that is not good enough," said the Argentinian.
"Sometimes, in our team, that can make the difference. We have great football players with the ball - but we need the ball. And to get the ball, we need to be winning that tackle. That is an important point."
And Newcastle attacking midfielder Georginio Wijnaldum has backed his skipper claiming his team-mates must show more hunger in front of goal before they can climb clear of the drop zone.
"Maybe we are too polite in front of goal," said the Dutchman. "We don't miss on purpose of course, but we must be greedier to get goals. We need to make life easier for us."