Lukaku has made 45 appearances for United since his move from Everton last summer, scoring 26 goals and registering eight assists.
It has always been a matter of time before City formally clinch the title but next week's opponents head into the derby in second place and with a win under their belt after beating Swansea City 2-0 at Old Trafford.
Romelu Lukaku sets Premier League record: The Belgium worldwide received plenty of stick during the festive period, where he struggled to find the scoresheet on a regular basis.
The 24-year-old was pleased with the team's performance against Swansea, especially with the energetic style in the first half. However, once again they had to call upon their goalkeeper to save them.
"We have to focus on the Champions League, we have United in the middle but for the line-up we have to think about the Champions League", the Spaniard told reporters.
It was an important win for United, who reclaimed second spot in the Premier League table from Liverpool, who had beaten Crystal Palace 2-1 earlier on Saturday, and the Red Devils now lead the Reds by two points, despite having played a game less than their arch-rivals.
"The first half was flawless".
David de Gea was barely needed, but he was after an hour with two superb saves from Tammy Abraham.
The two Portuguese tacticians, who reportedly did their coaching licences together, are extremely close and their bonhomie was evident from kick off on Saturday. "At Chelsea he was obviously young but he got experiences at good clubs before he arrived at Manchester United and then mentally he is more than ready".
Sanchez slid on his knees in celebration towards the 3,000 Swansea fans.
Raheem Sterling slotted home the third after fine work from David Silva and the hosts never looked like mounting any sort of fightback, despite Bolasie's second-half consolation.
"We let it go a little bit". I could feel the intensity went down. "Our passing was slower".