Samba gave away a penalty in the opening 10 minutes by tripping Ashkan Dejagah before losing possession for the Bulgarian's second goal of the night, and Berbatov said the nerves were evident early on.
"Yeah, you can see [players are nervous] sometimes," Berbatov told Sky Sports. "In the first couple of minutes you can see which players look nervous or [who] is having a bad game.
"So you try to push and press on them, which was the case with their player when we scored the second goal. You need to be clever in a situation like this because if you take advantage of them like you should, we score."
The Cottagers took a three-goal lead before QPR got back into the game, but with a penalty save by Mark Schwarzer and Steve Sidwell sent off late on, Berbatov stated that "childish mistakes" almost cost them.
"We weren't nervous but we almost threw the game away," Berbatov said. "We had a comfortable lead in the first half - three goals is a lot - and the something in the second half, a bit childish maybe.
"They scored the second goal and started to believe. But in the end we held onto the three goals we scored. We could have scored more but in the end three points was good for us.
"The only time they can score is when we make a mistake, so the goal for them lifted their spirits. If you look back, you see mistakes and try to correct them next time, but now we're going to celebrate the three points.
"I think you should give [the man of the match award] to [Schwarzer], or I will be giving it to him in the dressing room, because it's not the first time he's saved a penalty.
"He's a great goalkeeper and without him I don't think we were going to win this game."
Berbatov also stated that he is enjoying life at Fulham, and refuted suggestions that the club were ever in danger of relegation.
"It's great, I'm enjoying my football here. You can see it on the pitch, by the goals I score and the way I'm playing. It's going great for me, and for the team, so I hope it continues this way," Berbatov said. "We've always been safe. I don't see why anyone should worry. We play good football and sometimes we make childish mistakes which is why we suffer, but if we correct this we will be even better."