The Ibrox club secured their place in the last eight after defeating German outfit Werder Bremen 2-1 on aggregate.
And Bain said Rangers were confident of going further in the tournament.
"Sporting are a club with a decent heritage and I'm sure Walter Smith will be taking them extremely seriously," he said.
"At this stage of the competition, all the teams are of a level, but we have had a good European campaign.
"We came up against the best team in the Champions League and narrowly missed out on qualification.
"Then we played the second-placed team in the Bundesliga and we managed to see them off."
Rangers were delighted to be competing for four trophies at this stage of the season, Bain added.
In the other quarter-final ties, Bayer Leverkusen take on FC Zenit St Petersburg, Bayern Munich face Getafe and Fiorentina versus PSV Eindhoven.
The semi-finals will take place on 24 April and 1 May, with the final scheduled for 14 May at the City of Manchester stadium.