As a two-time winner of the Champions League during his playing days with Juventus and Borussia Dortmund, Sousa knows plenty about European pedigree.
And despite masterminding a 2-1 victory over the Swiss outfit in the home leg last month, Sousa remains wary of Basel's stature having seen them reach the last 16 of the continent's top competition, the Champions League, last term.
The sides meet again at St Jakob Park on Thursday, with the Portuguese coach deferring to the hosts and declaring them favourites to progress in top spot.
That goes against current form, with Basel only mustering two points from their first three matches to lie third, but Sousa was unequivocal.
"I said already at the time of the draw that I see the FC Basel at the top of this group," he said.
"The club has a lot of experience at this level, and last year they returned to big things.
"The start of the season was not so good for them, but Basel is still a strong team."
Basel reacted decisively to their dip in form, sacking manager Heiko Vogel and installing Murat Yakin.
Yakin's second game in charge was the defeat to Videoton but since then he has overseen impressive wins over FC Zurich and Young Boys.
"Since the coaching change, the team played with a lot more motivation and increased the intensity," noted Sousa.