"I think our defence has been so poor and we've got to get that right. A couple of years ago our defence was the best in the league but now it seems to have dropped away and it's disappointing.
"We need to be physical with these guys."
"We need to stop them getting good quick ball which limits their options for attack and if you stop the first one, the next one is slower and maybe you can win the ball back," stated Best.
With only two wins from 11 games, bottom of the Magners League and out of Europe, it's not surprising morale is low in the Ulster camp and they are desperate for a victory to lift the mood before derbies with Leinster and Munster over the festive period.
"If I was to say it's not having an effect on me I'd be lying as it clearly is, I don't like it when the team does badly," added Best.
"I'm a professional and everybody here is a professional, rugby is a massive part of your life and when it starts going badly your life breaks down around it and it's disappointing because we are in control of that and need to sort of ourselves out.
"It's not as if we haven't been working as hard or trying as hard. Things are just aren't going well in defence where we're missing tackles and falling off people which is giving them front foot ball. It's things like that we need to get right.
"There are times after the game and during the week when I find it difficult to sleep thinking about what's gone wrong with the team and how we can get ourselves out of it. Everybody feels like that.
People really don't appreciate how hard it hits us and think we don't care, I feel bad for Rory as captain he bares a lot of the responsibility and he have got to just play for each other and try to win this game," continued the Irish flanker.
Ulster have lost their last two home games again Gloucester and Edinburgh, the fans have been quite vocal in their criticism of the team and Best can fully understand the frustration and wants to put on a show for the Ravenhill faithful against the Ospreys.
"The competition is over for us but that's not saying this game isn't important, we need to get a win and then get a win against Leinster to start building some momentum especially as we have been performing badly at home.
It's sickening to let ourselves and the fans down. We've got good supporters and I don't like looking over and seeing them leave with 10 to 15 minutes to go. We don't want that to happen."
"We'll be judged by our actions tomorrow night and I just hope the fans get behind us," continued Best.