The Manchester United defender could be out for up to six months.
The 20-year old rose to prominence during Pochettino’s stint at Southampton and now faces a long lay-off after a tackle from another of the Argentine’s former players, Hector Moreno.
“It’s always difficult because he was crying, which is normal,” said Pochettino, in quotes published by the LES.
“You can understand after a big injury, not only for the pain but everything to do with the situation. It’s always a difficult moment for a player.
“He is much better today but I feel very sorry for him. It had a big impact on me. I watched the moment happen and I felt sick after I saw it. I can I can only give my support and wish a speedy recovery but now it’s about thinking of recovery as soon as possible after his injury.”
“It was never the intention of Hector Moreno to do this but that is football. There is always danger and sometimes this kind of thing happens. It was unlucky for Luke,” he added.
Shaw’s injury further compounded United’s misery in a night which saw them lose their Champions League opener against PSV Eindhoven despite dominating proceedings for much of the game.
Memphis Depay gave United the lead against his former club before villain of the day Moreno equalised just before half-time.
Luciano Narsingh tipped the game in PSV’s favour in the 57th minute and the Dutch champions held on for all three points.
Louis van Gaal now faces an issue - with no natural cover at left-back available - while Roy Hodgson will also have concerns given Shaw’s emergence as England’s first choice.
Pochettino’s current left-back Danny Rose is one player who stands to gain from the United man's misfortune, after being overlooked by the England manager in recent squads.