They may not have been pretty to watch, but it proved effective, leaving the Red Devils only four points clear of second-place Chelsea, whose game in hand is at Newcastle United on Sunday lunchtime.
It could even have been worse for United had referee Peter Walton awarded Boro an injury-time penalty after substitute Dong-Gook Lee appeared to be brought down by John O'Shea in the box.
United had a perfect start with a goal in the third minute.
The brilliant Paul Scholes produced a magnificent 40-yard defence-splitting pass to send Wayne Rooney clear of the Boro backline.
Rooney coolly rounded Mark Schwarzer as the Boro goalkeeper came off his line to meet him, but the England man let the ball run on to Kieran Richardson, who scored with a simple left-foot tap-in from close range.
United failed to capitalise on their early advantage against a team which has proved a constant thorn in their side at Old Trafford.
United's play became sloppy and they suffered a massive blow just before the interval.
With five minutes to go to half-time, Rio Ferdinand pulled-up with a recurrence of the groin injury which kept him out of Tuesday's home game against Sheffield United.
Ferdinand tried to hang on for the interval - a decision which played a part in Boro's equaliser.
With the game a minute into first-half injury time, the England defender was a mere passenger when Yakubu Ayegbeni found Stewart Downing free on the left side of the United box.
Downing provided the perfect teasing cross to the near post where Mark Viduka powered in before Wes Brown to head home from four yards.
Ferdinand was replaced by Ryan Giggs at the break and Richardson, enjoying one of his best games for United, made way for Darren Fletcher.
With O'Shea alongside Brown in the centre and Fletcher at right-back, United's defence looked vulnerable against the physical strength of Viduka and Yakubu and Downing's guile wide on the left.
But it was at the other end where United's hopes faltered and died.
Ole Gunnar Solskjaer replaced the ineffective Alan Smith in the 67th minute, but Schwarzer was rarely troubled.
Solskjaer, Rooney, Cristiano Ronaldo and Michael Carrick all missed chances, although it was Giggs who came closest when his goal-bound shot was superbly blocked by George Boateng.
But United's Edwin Van der Sar was the busier of the two goalkeepers.
He denied Viduka a second goal early in the second half, saving with his knees after the Australian had easily slipped Brown's clutches.
Then, in the 58th minute, he repeated the save to keep out Yakubu's shot after he had beaten O'Shea.