Johnson was destroyer-in-chief, taking four for 61, with England losing six wickets for only nine runs in 11 afternoon overs.
That allowed Australia to bowl England out for 136 before they closed on 65 without loss to establish a daunting lead of 224 runs in Brisbane.
Haddin told Sky Sports 2: "It was obviously a tough day but we had to earn the right to get those wickets in the middle session and I think we built some good pressure up leading into that wonderful hour-and-a-half in the afternoon.
"The game's in a good position with three days to go.
"There was a plan to go short, especially when the tail came in and we might as well use guys like Mitchell Johnson who do have that extra bit of pace.
"We know it's quite a hard ground to bat on when the ball's going around you so we executed those plans pretty well today."
Despite their remarkable collapse, the mood in the England dressing room remains "pretty positive", according to batsman Michael Carberry.
The Hampshire left-hander was the tourist's leading light, top-scoring with 40 before falling to Johnson, and feels it is too early to write England off in the battle to win the first Ashes Test.
"I think the batsmen obviously feel a little down about the session but the feeling in the dressing room is still pretty positive," he said.
"We know there's still three days to go in the game so we're not totally out of it yet, so we'll come out tomorrow hot.
"Credit to the Australians - they bowled well. We never really got away from them at any stage.
"It's easy to say that (we allowed them to bowl at us) but if people put balls in the right areas then it's going to be difficult to score.
"I guess you have to try and be proactive as a batsman while respecting good bowling."