Despite a string of second half chances, Boro were beaten on a rainy day at Hull City.
Neil Warnock named an unchanged side from that which beat Sheffield United in midweek, but only six substitutes were included on the teamsheet, including young left-back William Kokolo.
The hosts started in lively fashion, George Moncur firing a free-kick wide from a tight angle, and Di'Shon Bernard seeing a deflected effort parried away by Joe Lumley.
Sol Bamba was forced into a brave interception as the physical Tom Eaves looked to turn and get a strike away at Boro’s goal.
As the first half wore on, Boro began to gain a handle on the contest. Marcus Tavernier was denied from close range by City keeper Matt Ingram after Marc Bola had fired a low cross his way, then he turned provider with a through ball for Andraz Sporar which the striker smashed over.
In the second half, and as the rain continued to lash down, it was Warnock’s side who continued to turn the screw.
Duncan Watmore saw an appeal for a penalty waved away when he broke into the box and went down under a challenge, and Marc Bola saw a drive shot blocked away by the Tigers defence.
Watmore was involved again as he turned Marcus Tavernier’s pass back to the midfield man in the City area, but Tavernier sliced wide.
Two more gilt-edged chances came and went for Boro, first Sporar slotting the wrong side of the post after latching onto a superb through pass from Matt Crooks, then Paddy McNair drawing an excellent save from Ingram when Sporar nodded invitingly into his path.
Then came the sucker punch. Eaves had volleyed wide after stealing in behind in a warning sign to Boro, and to was another volleyed effort that did the damage, Keane Lewis-Potter’s effort rebounding off the upright, hitting Joe Lumley and finding the net.
Boro went pushing in search of an equaliser, and there was a moment of confusion as McNair stroked a free-kick into the top corner, only for the referee to blow for an infringement spotted during his run-up.
And a drab day was made worse for Boro when Mallik Wilks took advantage of Boro’s forward pushing and added a late second on the break.