Middlesbrough missed the opportunity to overhaul leaders Southampton as they suffered a comprehensive defeat by Blackpool at Bloomfield Road.
Following a goalless first half, Matt Phillips put the Seasiders ahead after Barry Robson had hit the post for Boro.
Lomana LuaLua doubled their lead before Seb Hines came off the Middlesbrough bench to turn into his own net.
The win sees Tony Mowbray's side slip to fourth while Blackpool move to within a point of the play-offs.
Southampton's defeat at Brighton had opened the door for Boro to leapfrog them with victory over Ian Holloway's men.
But it was Blackpool who were the more ambitious of the two teams in the first half, with Thomas Ince linking up with LuaLua and shooting narrowly wide, before forcing an impressive stop from Boro keeper Jason Steele.
Middlesbrough's best chance of the half came when Scott MacDonald burst clear and rounded keeper Mark Howard only for defender Craig Cathcart to clear off the line.
The visitors started the brighter after the break but it was Blackpool who went ahead with Phillips ripping through the Boro defence before finding the bottom corner.
Tangerines full-back Alex Baptiste dispossessed Joe Bennett and had a shot saved, only for LuaLua to collect the rebound and double the lead.
Faris Haroun netted for Boro, but his effort was disallowed, before his team-mate Hines put the result beyond doubt, diverting Phillips's cutback into his own net just two minutes after coming onto the pitch.
Blackpool boss Ian Holloway: "I can't remember too many more exciting afternoons than that.
"Tom Ince and LuaLua were a box of tricks every time they had the ball and Matty Phillips is playing out of his skin at the moment - he's added end product and goals to his game so well done to him.
"I thought the front three were superb and Angel (Martinez) in midfield came in like he'd been playing all season and I felt we had great balance in midfield with Chris Basham and Ludovic Sylvestre as well."
Middlesbrough manager Tony Mowbray: "I don't think the result was flattering towards them at all. Three days ago they were sitting on the back of a 3-0 defeat and that would have hurt them an awful lot.
"I don't have any complaints to be honest. Their front three gave them some individuality and when we conceded just after hitting the post it made things very difficult for us."