Boro were left rocked at the Riverside after Preston staged a smash and grab raid to steal the points on Teesside.
New boss Chris Wilder will have learnt plenty about his new charges after seeing them dominate much of the game before conceding twice late on to finish up losing.
Leading 1-0 after half-an-hour and playing some good stuff, Boro paid the price for not converting chances when Preston suddenly threatened late in the game.
The visitors did have a couple of decent early chances, but once Boro settled into the game, it was Wilder’s side who enjoyed the territorial advantage.
Paddy McNair had a corner punched away and when Isaiah Jones did well down the flank, Duncan Watmore had a shot blocked. Matt Crooks also had a shot blocked by the head of Josh Earl after good work by Marc Bola.
Preston were a threat on the counter and Marcus Tavernier made a superb tackle to deny Alan Browne what would have been a great chance for the visitors to take the lead.
Jonny Howson, making his 200th Boro appearance, did well to release Bola, whose cross was cut out with Watmore waiting. Watmore also came within inches of getting the decisive touch on a wonderful ball in from Tavernier.
Boro were in front shortly after the half-hour mark when McNair showed great movement to get on the end of a Howson corner and headed the ball into the top corner.
Wilder’s side played some good stuff and Watmore almost made it two before half-time, but he was denied by a good reaction save from Daniel Iversen.
Lee Peltier went even closer at the start of the second half after more good build-up play. The Boro defender drilled a shot which Iversen could only deflect against the bar before it bounced to safety.
Moments later, Crooks and Jones linked up well with the latter’s finish going over the top.
Iversen was called into action once again when McNair won a free-kick on the edge of the box and stepped up to force the keeper into action with a sweetly struck set-play.
Substitute Onel Hernandez was next to test Iversen when he showed great feet inside the box to work an opening to drill a shot against the keeper’s legs. And when Andraz Sporar drilled an effort goalwards Iversen got down well.
The visitors were unable to make any headway, but after Luke Daniels was called upon to punch away a ball into the box, Tom Barkhuizen saw a shot deflected for a corner.
As the clocked ticked down, Jones sent a left-foot strike over the top as Boro continued to search for a second goal to kill the game off.
The one-goal lead was always going to be tested and when Sol Bamba made a vital block to prevent a great chance, Ched Evans was able to head home the resultant corner with 13 minutes remaining.
And five minutes later came the sucker punch. Boro failed to deal with a routine ball in the box and Emil Riis was presented with a great opportunity to turn the scoreline on its head.
Immediately before that, there had been a huge penalty shout by Boro when a Tavernier shot appeared to strike Browne on the arm, but referee Andy Woolmer remained as unmoved as he did when Preston shouted for two different spot-kicks during the first-half.