Heung-min Son says Tottenham’s first defeat under Jose Mourinho was particularly painful because the ­players know they can do better.

Mourinho’s much-anticipated return to Manchester United was ruined by Marcus Rashford’s double as Spurs went down 2-1, losing for the fifth time in the Premier League this season to leave them nine points behind fourth-placed Chelsea.

Mourinho’s successor Ole Gunnar Solskjaer was under pressure ahead of the match following draws against Sheffield United and Aston Villa.

Spurs, however, were second best at Old Trafford and had goalkeeper Paulo Gazzaniga and Dele Alli’s sublime goal to thank for keeping the scoreline respectable, as Mourinho’s winning start came to an abrupt halt.

With Burnley next up on Saturday at the Tottenham Hotspur Stadium, Son insists there is no time for the players to lick their wounds.

“I feel hurt and pain,” said Son. “Last night was very sad and I didn’t want to talk with anyone afterwards but I have to be positive. This kind of game against big teams like United or [Manchester] City, you want to win.

“I feel more pain because we know we can do better, I know I can do better. That’s why I feel more pain than other games. We know we have to do better but I just want to take the positives — three wins in a row [under Mourinho].

“This kind of impact we have to take forward. Sometimes you win and ­sometimes you lose but we have to do better. Now we have to compete again against Burnley. This is the most ­important thing now.

“It’s not time to be disappointed or sad because we have another game in three days. We have to carry on ­working hard. It’s important to look forward, so we can make it better.

"This is up to us and we have to be focused on this game. Every single team plays every three days so this can’t be an excuse.”

Mourinho revealed on Tuesday that he is “in love” with the South Korean forward, who scored the first goal of the Portuguese’s reign, against West Ham, last month.

“I’m looking forward to working with him,” said Son. “I’m still learning so many things about him. I think I can learn from him and I’m still hungry. It will be better and I look forward to working with him. It’s an honour to work with this manager.”

Alli, who equalised brilliantly between Rashford’s goals early in each half, admitted “arrogance” was a factor in Spurs’ abject display.

“We lost not on them outplaying us but on our attitude — we weren’t ­hungry enough,” said Dele. “It was maybe arrogance and over-confidence.

“In games like this you have to have a bit of arrogance but we were sloppy.”

Mourinho said his former club were deserving winners.

“I tried to tell the players exactly the way United approach these matches they have at home, against Liverpool and Chelsea, always strong starts.

“We have to blame ourselves. United must obviously be happy with the points and overall they deserve it.”