Manchester United's lead over Manchester City is down to four points from six after the Premier League leaders were held 1-1 at Swansea City's Liberty Stadium on Sunday.
Patrice Evra struck with a first-half header to put United on their way but a Michu equaliser before half-time was enough to give Swansea a richly deserved point.
Having seen neighbours City cut their lead at the top of the league to three points with Saturday's last-gasp 1-0 victory over Reading, United were keen to restore their healthy advantage going into the busy festive period.
United winger Antonio Valancia had an early cross blocked by Ben Davies but it was Swansea who looked the more likely in the early stages, with Nathan Dyer putting in a dangerous cross and Michu spurning a sight of goal.
The Spaniard, who now has 13 goals in the league this season, fired high and wide under pressure from Nemanja Vidic, but the threat was clear.
Wayne Routledge tested David de Gea with a shot on the turn from 18 yards before Michu was caught offside from a delightful through-ball by Routledge.
The danger for United was always there and though Swansea came into the game on the back of successive defeats against Norwich City and Tottenham Hotspur, they were not short on confidence.
Clearly smarting from a sluggish start, United might have taken the lead in the 14th minute when Michel Vorm, back in the Swansea goal after a two-month injury lay-off, beat away Wayne Rooney's 25-yard strike.
Two minutes later, Evra rose to head home Robin van Persie's near-post corner.
It was the signal for United to step on the gas and try to kill off the game before Swansea could respond.
Van Persie and Valencia were the main source of Swansea's problems, though Rooney almost latched onto Ashley Young's crisp centre after van Persie had torn a hole in the home midfield.
Then, as United dropped their guard, Swansea struck.
Routledge sent in Jonathan de Guzman and though his shot was kept out by De Gea, Michu arrived with perfect timing to make it 13 for the season.
Swansea were good value for the goal and though the sides turned around level, De Guzman and Michu both had opportunities to send the hosts in at half-time with a lead.
United were strangely careless in the second half, with Rooney, on too many occasions to remember, giving away the ball in positions of promise.
His free-kick on the hour, after Chico Flores was booked for a poorly timed tackle, was straight at Vorm, as was Dyer's 30-yard shot at the opposite end a minute later.
The introduction of Javier Hernandez gave United a little more bite, with Rooney dropping back into the visitors' four-man midfield.
From that juncture, United began to dominate possession, with Swansea needing all of their resolve to keep the leaders at bay.
Van Persie, who was booked with Ashley Williams after the pair had a spat on the edge of the 18-yard box, struck the crossbar with a volley from Rooney's centre and Vorm pulled off a smart save from Hernandez.
Michael Carrick then forced a great save from Vorm and Swansea twice had to produce desperate blocks as United turned the screw.
Swansea, however, held on to claim a first ever Premier League point against United.