Belgium's Jan Vertonghen listens to questions during a news conference
Vertonghen started Belgium's Euro 2016 opener against Italy at full-back, a 2-0 defeat.
Italy's Marco Parolo in action with Belgium's Jan Vertonghen
Whether he continues at full-back or switches to centre-back, he knows he will be in for a tough time against Long, who ended the season in good form for Southampton.
Vertonghen said: "For me he is the main man for them. I find him one of the best strikers in the Premier League.
"He is very mobile, very direct, and he has a good head. Hopefully we can stop them [Ireland]."
Shane Long scores the first goal for Southampton
Vertonghen's Belgium and Tottenham teammate Toby Alderweireld also spoke of Long's talent, telling Nieuwsblad: "He's fast and strong. The game system of Ireland is ideal for him. It will be difficult for us."
Long is not the most exciting player Spurs could sign this summer, but if their transfer pursuits did end up with them signing the Irishmen, their key defensive duo would certainly approve, and their battle with him at Euro 2016 will be fascinating to see who comes out on top.
Sweden's Andreas Granqvist in action with Republic of Ireland's Shane Long