Cape Town - Alexis Sanchez scored his first goal for Manchester United as Jose Mourinho's men took advantage of a rare slip-up from Manchester City to close to within 13 points of the league leaders with a 2-0 win over Huddersfield Town.
City were made to pay for an extraordinary miss by Raheem Sterling as they dropped points for just the fourth time in the Premier League this season in a 1-1 draw at Burnley as Johann Berg Gudmundsson's equaliser eight minutes from time cancelled out Danilo's spectacular opener for City.
United manager Mourinho conceded his side were playing for second place after falling 15 points behind City with defeat at Tottenham Hotspur on Wednesday, and showed his displeasure at that performance by dropping star midfielder Paul Pogba to the bench among four changes.
A minute's silence preceded kick-off at Old Trafford as United paid tribute to the victims of the Munich disaster 60 years on from the tragedy that killed eight of the great United Busby Babes.
Mourinho had called on his players to mark the occasion by bouncing back in style, but the hosts had to wait until 10 minutes into the second half to make the breakthrough when Lukaku got across his marker to volley home Juan Mata's cross from the left for his 19th goal of the season.
Sanchez was then given the chance to cap his home debut 21 minutes from time when he was brought down just inside the area Michael Hefele.
And much to the Chilean's relief, he tapped home the rebound after Jonas Lossl had saved his initial effort from the penalty spot to open his United account after joining from Arsenal on reportedly the biggest ever contract in Premier League history.
City pay for Sterling miss
City were made to rue a slew of missed chances, most notably when Sterling failed to turn Kyle Walker's low cross into an unguarded net from point-blank range as Burnley salvaged a valuable point despite seeing their winless league streak extended to nine matches.
"Of course we are frustrated in terms of the result but the performance was outstanding against a Burnley side who are the most British of teams in terms of long balls and the way they play," said City boss Pep Guardiola.
"But football is about goals. We needed to score the second, third and fourth when we had the chance. When you arrive in the last 15 minutes at Burnley 1-0, this is what can happen."
Leicester City missed the magic of star man Riyad Mahrez as they failed to beat Swansea City at home in a 1-1 draw.
The Algerian hasn't trained since Leicester priced Manchester City out of a move for Mahrez on transfer deadline day on Wednesday.
Jamie Vardy smashed the hosts in front, but Swansea's rise under Carlos Carvalhal continued as they extended their unbeaten run to seven games thanks to Federico Fernandez's equaliser to edge out of the bottom three on goal difference.
In a big day in the battle to beat the drop at the bottom of the table, Southampton recorded their first win since November, 3-2 at West Brom, to move out of the relegation zone and up to 14th.
West Brom paid tribute to club legend Cyrille Regis, who died at the age of 59 last month, before kick-off and got off to a flying start through Ahmed Hegazi's header.
However, three quickfire goals from Mario Lemina, Jack Stephens and James Ward-Prowse either side of half-time put Southampton in charge before Salomon Rondon's consolation for West Brom, who remain bottom.
Brighton also bagged their first league win in seven games thanks to goals from Glenn Murray, Jose Izquierdo and Pascal Gross to beat West Ham 3-1.
And Bournemouth moved up to ninth as they came from behind to beat Stoke City 2-1 through strikes from Josh King and Lys Mousset in the final 20 minutes to drop Stoke back into the drop zone.