There is an unwritten rule that states that players given the greatest exposure ahead of a big game seldom feature most prominently in the headlines the next day.

While we were busy building up Ryan Giggs for potentially the 1,000th appearance of his professional career, or ruminating on the chances of Robin van Persie being selected to face Norwich City after shrugging off a hip injury, or pondering whether Wayne Rooney would be recalled to the Manchester United starting line-up, we should have known that a completely different name would end up in the spotlight.

And so it was that a hat-trick from Japanese star Shinji Kagawa condemned the Canaries to defeat at the hands of the Premier League leaders at Old Trafford and gave United a 15-point advantage at the top of the table.

True, Rooney scored an exquisite fourth goal in the final minute to wrap up a comprehensive victory, and played a major role in two of Kagawa's three goals, but while the England striker was the outstanding individual on show, it was the summer import from the Bundesliga who attracted banner headlines such as 'Kaga-doo doo doo'. As long as we don't have to listen to the song.

For Chris Hughton's men, the final 15 minutes proved something of a galling experience after they had battled manfully and, with one exception in first-half stoppage time, successfully, to keep United's international brigade at bay.

While the hosts had the lion's share of possession in the opening half, City goalkeeper Mark Bunn was seldom directly troubled, other than getting Van Persie's boot in an uncomfortable place diving at the Dutchman's feet after he played a one-two with Rooney, and gathering a tame effort from Michael Carrick.

That was until time added on before the interval, when United went ahead with a soft goal. Antonio Valencia crossed from the right, Van Persie flicked the ball past Sébastien Bassong and Kagawa appared to slice his shot just enough for it to slither inside Bunn's left-hand post.

City reacted well after the break and, on 62 minutes, Russell Martin appeared to miss a golden chance to equalise when Grant Holt nodded down Anthony Pilkington's cross to the far post, but the full-back hooked his shot over the bar with the goal at his mercy – only for referee Swarbrick, who has a weather-vane arm where Norwich are concerned, to penalise Holt for a foul on Evra.

Both sides made changes but before City's Kei Kamara or Elliott Bennett could get into the swing of things, it was game over on 76 minutes when Kagawa struck his second of the match.

Carrick's long pass forward was brilliantly brought under control by Rooney and he stepped inside Bassong to roll the ball into Kagawa's path for a simple finish.

Bunn made a fine save from Danny Welbeck as United threatened a third, but still it came, with three minutes left. Once again it was made in England, finished in Japan, Kagawa flicking his shot over Bunn after another Rooney pass. City were ragged by now and in the final minute, Rooney, fittingly, floated in a magnificent fourth goal from Welbeck's pass to have the final say.