The north London club failed in a deadline day bid for the 26-year-old Portugal international during the summer transfer window as they sought to replace the influential Luka Modric, who departed for Spanish champions Real Madrid.
With the club not in action until Thursday evening against Panathinaikos, Villas-Boas took the opportunity to watch Paris Saint-Germain beat Porto 2-1 in the French capital, with the manager attempting to play down the visit as anything out of the ordinary.
"Whenever Porto are close to the place where I am, I go see them," Villas-Boas told the Daily Mirror.
"I went to see them last season against Manchester City and took the opportunity to go and see them again against PSG.
"It was a tiring trip, but good to see people that are important to me."
Tottenham sit in second place in Group J and should they avoid defeat against their Greek opponents at White Hart Lane, they will qualify for the next stage of the Europa League, along with Lazio.