Son was devastated after his challenge left Everton midfielder Andre Gomes needing surgery on a broken and dislocated ankle during Sunday’s 1-1 draw at Goodison Park.
The South Korean was sent off, a decision which has since been overturned by the Football Association, and the club have been providing support for him.
But he travelled to Belgrade and Pochettino says he is in good form.
“Son was devastated after the action,” he said. “It was a mix of everything, it was a mix of the injury, a mix of the red card, the situation of the game it was an emotional moment for everyone.
“Now after a few days, everyone is available to play. He is in a very good way, he feels sorry like everyone, but he is in good form.”
Son will need to be on top form as Spurs take on Red Star Belgrade a year to the day that the Serbians beat Liverpool in last season’s group stage.
The atmosphere will be hostile, but it is hoped that fan behaviour will not cross the line into racism.
Spurs were subjected to abuse on their last trip to the Serbian capital while Red Star fans were banned from the reverse fixture a fortnight ago after racist abuse in a qualifying round.
The Serbia national team must also play a game behind closed doors following racism in the Rajko Mitic Stadium last month – the ground where Pochettino’s side will play.
Harry Kane says his side are ready to follow the protocol if things turn nasty.
Kane has recent experience of the three-step process following the shameful scenes in Bulgaria last month, where England were close to coming off the pitch in Sofia after some abhorrent abuse.
Red Star are keen to avoid any issues, posting a video on their Instagram page, while their coach Vladan Milojevic promised there would be no problem.
Kane is hoping he is not at the centre of a storm again, but says the club are ready if the worst happens.
“Like I said before that game (in Sofia), hopefully it doesn’t happen and we play a football match.
“If it does happen then obviously there’s a protocol in place like there was in Sofia, and as players we follow that.”
Milojevic said in his pre-match press conference: “I can guarantee that everyone here will feel safe.
“In our team we have players with different skin colours and never had a problem. Not even Tottenham footballers will have them tomorrow.
“We will show that we are the real hosts and that this is a country that embraces diversity.
“I believe that our fans will be great tomorrow and I urge them to come as much as possible to support us.”