Preston midfielder Paul McKenna has revealed it has taken some time for the players to realise they are in the Championship play-offs.North End face Sheffield United in a two-legged semi-final after securing a top-six spot against QPR on Sunday. [LNB]"We couldn't believe we actually managed to qualify," McKenna told BBC Radio Lancashire. [LNB]"It's a massive bonus to get in there and we're just thankful we've got a bite at the cherry." [LNB]McKenna, 31, was a member of the Preston squad who lost play-off finals in 2001 and 2005.[LNB] We want to play everything down and get on with our job and basically keep under the radar Preston midfielder Paul McKenna And despite having won their last four games, the Chorley-born player accepts they are facing another tough challenge this time round [LNB]"We've got a bit of momentum coming into these games," he said. [LNB]"But Sheffield United have lost only once in 13, so they're really strong. [LNB]"It's a massive ask and for us to say our name is on the trophy, there's a lot of football to play before that." [LNB]Despite being rank outsiders of the four clubs vying for promotion, McKenna said that will suit North End mentally. [LNB]"We're happy to go in as underdogs as we have been for the last two or three months," he said. [LNB]"We want to play everything down and get on with our job and basically keep under the radar." [LNB]BBC Radio Lancashire will broadcast full commentary of Friday's first leg, with build-up beginning at 1800 BST.