Both sides are desperate for points at the Liberty Stadium to ease relegation fears.
Britton said: "This game is so important for us - and for Fulham.
"We've had a difficult run of games against teams at the top of the table, but the next few games are against sides around us and those are the games you have to win.
"It's almost like a cup final. They're the games you talk about, we've got to get the three points and stop them getting any to make sure we pull away.
"These next four games will define our season. After them, we will know exactly where we stand."
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