Boro were once again made to pay in a quickfire second half spell as Luton Town came away winners on Tuesday.
The Teessiders took the lead in the first half through youngster Josh Coburn, but three goals in five second-half minutes swung the game the Hatters’ way.
Neil Warnock had made four changes from the side that lost to Birmingham City at the weekend - out went injured duo Martin Payero and Uche Ikpeazu, while Joe Lumley and Lee Peltier dropped to the bench.
In came Luke Daniels for his first Boro appearance between the posts, Anfernee Dijksteel returned from injury, Isaiah Jones was back in the XI, and Coburn made his first league start up front.
The Teessiders appeared to have taken the lead with 12 minutes on the clock when Marcus Tavernier converted from close range, but the assistant’s flag was raised for a goal-kick as Jones hooked back into the danger area moments earlier.
It was to be 1-0 to Warnock’s side three minutes later, courtesy of an incisive move and a clinical finish. Matt Crooks sprayed a pass into the channel for Andraz Sporar, who fired across goal invitingly for Coburn to slide home.
For the Hatters, Harry Cornick was the dangerman, and he squandered the first of three chances to fall his way in the first half when he found space in Boro’s area but slipped at the vital moment.
There were huge appeals for a Boro penalty when Jones got around James Bree and was brought tumbling down, but a goal kick was the referee’s signal.
Then it was back to Town on the offensive, Cornick sending one curling effort over the top then later prodding wide with a golden chance when the ball broke his way just outside of the six yard box.
There was a key piece of defending to preserve Boro’s lead going in at half-time as Jonny Howson hooked a bobbling ball off the line and away from danger.
But as had been the case against Birmingham a few days earlier, though, a disastrous second-half spell would prove costly.
Boro conceded a cheap corner, and when it was swung into the area by the Hatters, captain Sonny Bradley was unmarked and unchallenged as he rose to head home.
Three minutes later, Town had turned the game on its head, Paddy McNair getting a block to Elijah Adebayo’s first effort but the striker persisting to turn home their second goal.
And to compound things, just two minutes after that Cornick did get on the scoresheet, capitalising on a sloppy pass from Tavernier before finding the bottom corner.
Tavernier tested Simon Sluga with a free-kick fired at his near post, and substitute Jamaes Lea Siliki sent one skimming wide, but there was to be no comeback for the travelling Teessiders.
Boro: Daniels, Dijksteel, Tavernier, Hernandez (Kokolo 83), Sporar (Watmore 68), Howson (c), McNair, Bamba, Crooks (Lea Siliki 77), Jones, Coburn
Subs: Lumley, Olusanya, Peltier, Sivi
Luton Town: Sluga, Bree, Potts (Onyedinma 55), Naismith, Bradley (c), Cornick (Hylton 81), Adebayo (Jerome 89), Burke, Mpanzu, Lansbury, Osho
Subs: Shea, Rea, Campbell, Muskwe
Attendance: 9790 (987 Boro)