Gus Poyet's side remain bottom of the Premier League with four games remaining, but have given themselves hope after taking four points from trips to Manchester City and Stamford Bridge.
Sunderland followed up their 2-2 draw at the Etihad with an improbable 2-1 triumph in west London last weekend, the first time the Blues have lost at home in the Premier League under Jose Mourinho.
The Wearside club now stand three points from safety and have a game in hand on the three teams above them as they end their season with fixtures against Cardiff, Manchester United, West Brom and Swansea.
Johnson said: "On the back of Chelsea there is genuine belief inside the dressing room. You can feel the buzz. No one wins there under Mourinho so it has given all of us a massive lift.
"It is in our own hands again with three home games against teams in and around us.
"We could not really have asked for better and I'd certainly rather have our fixtures than some of the others."
Although their only remaining game away from home is at Manchester United, Johnson accepts they must improve on their recent Stadium of Light performances if they are to have any hope of avoiding the drop.
"It's at home where our problems have been," said Johnson.
"At times, we've played like a top-seven side but we've also been absolutely awful. Now we've got to take the form we showed in our last two away games into Cardiff.
"Cardiff can't come for a point like other teams such as Norwich and Crystal Palace did. They didn't even want to score so long as we didn't but Cardiff can't afford to do that."