Boro almost pulled off a deserved great escape act at QPR but were edged out 3-2 at Loftus Road.
Chris Wilder’s side were hit by a whirlwind opening from the home side, who were 3-0 up inside 40 minutes.
But Matt Crooks reduced the arrears with a vital header before half-time and a rejuvenated Boro came out all guns blazing in the second half and, after Marcus Forss pulled another goal back with his first for the club, were unlucky not take a point from the game.
Wilder made just one change from the side which started against West Brom on the opening day, Forss coming in for his full debut in place of Chuba Akpom.
The home side started brightly and were ahead after just 13 minutes. Chris Willock seized on some sloppy play by Boro and shrugged off two challenges as he charged towards goal before lashing the ball past Zack Steffen.
The USA international goalkeeper was also called upon to make a good save when Lyndon Dykes sent a powerful strike towards the top, but the hosts went and doubled their advantage from the resultant corner.
Jimmy Dunne was the man who nodded home the set-piece to put QPR 2-0 up inside half-an-hour.
The home side came within a whisker of furthering that advantage when Stefan Johansen seized on a free-kick quickly and tried an audacious attempt to chip the back-peddling Steffen from around 40 yards.
But there was worse to come for Boro on 38 minutes when QPR sent in a free-kick and Dykes found space on the wrong side of the defence to head home from close range.
Boro did reduce the arrears almost immediately, though. Ryan Giles sent over a corner from the right and Crooks headed the ball past Seny Dieng to make it 3-1.
And Wilder’s men almost pulled back another before the break. Duncan Watmore chased what appeared to be a lost cause before pulling the ball back for Forss, who saw his shot blocked by a QPR defender.
The Boro boss made two changes at the break with Akpom and Paddy McNair, who missed the opening game due to suspension, replacing Watmore and Anfernee Dijksteel.
The change almost paid immediate dividends. Forss escaped down the right and Akpom got the wrong side of the defender, but with Dieng at his feet, his shot was just wide.
Dieng was also forced into a quick reaction when Jonny Howson swung a teasing ball into the box, but the scrambling goalkeeper got a hand to the ball.
Moments later, he pulled off a fantastic reaction save from Akpom’s close range header as Boro looked a very different proposition to the opening 45 minutes.
Indeed, the arrears were deservedly reduced further on 55 minutes when Crooks teed up Forss for his first goal in a Boro shirt and the away end exploded with delight.
Two minutes later, it was almost level pegging. Giles sent over a good cross, but Howson couldn’t get his header on target.
There were appeals for a penalty just after the hour Marc Bola embarked on a driving run and Riley McGree saw his shot blocked by a QPR defender.
And when Boro did deservedly get the ball in the back of the net – McNair converting from close range – the goal was ruled out by an offside flag.
Boro fought and fought for an equaliser during the closing stages, but the clock eventually ran out for the Teessiders, who also had Darragh Lenihan dismissed in time added on for a foul on Macauley Bonne.
