A thunderous Jose Holebas strike was enough for Watford to win 1-0 at the Riverside Stadium on Sunday as Middlesbrough's return to the Premier League continues to falter on home soil.
The Teesside club have picked up a single point from 12 available on their own patch so far this season, having lost just twice in front of their home fans in winning promotion last term.
Holebas' exceptional strike was in stark contrast to the rest of the contest, a dull affair in which neither side managed to gain a foothold in attack.
Isaac Success replaced compatriot Odion Ighalo up front for Watford and was a constant menace, with Boro right-back Antonio Barragan somehow escaping a red card for a string of fouls on the visitors' club-record signing.
Karanka will now be feeling the heat, with Arsenal, Manchester City, Chelsea and Leicester City among Boro's next five fixtures, while Watford are into the top half on the back of their second away win of the campaign.
Boro had the majority of the play in a dreary first 45 minutes, but Heurelho Gomes went untested in the Watford goal.
Indeed, the half was most notable for the hosts' right-back Barragan avoiding a dismissal when he tugged Success to the ground, having been cautioned for an earlier foul on the Nigerian.
Though the opening period had passed without much incident, the second half was lit up by a moment of outstanding quality from Holebas.
Success again raided down Boro's right flank, and hit the deck under Adam Forshaw's challenge in the area. As the visitors protested to referee Roger East, Holebas reacted quickly to rob Cristhian Stuani 30 yards out and lash a swerving shot into the top-left corner past a helpless Victor Valdes.
Success had Barragan on toast again soon after, the Spaniard clumsily felling his man, but East once again failed to dismiss the ex-Valencia player.
However, Karanka finally saw sense and withdrew the right-back, while also introducing Adama Traore in a bid to spark his listless attack.
East ensured he would end the game with both sets of fans denouncing his abilities when Calum Chambers was bundled over when approaching the penalty area, with nothing given.
And the Riverside's crowds frustration was clear as Jordan Rhodes' 89th-minute introduction was sarcastically cheered before the final whistle was met with boos to complete a day of deep disappointment for 17th-placed Boro.