The Europa League theme tune may not have the recognition, or the hum-ability of its Champions League equivalent but it's music to the ears of Celtic and Rangers fans.

A season of domestic battle may lie ahead but the sprinkling of continental glamour is something to savour as the nights draw in. The stars of Lazio and Porto will be coming to Glasgow and there will be the usual dramatic twists and turns we're used to whenever Scottish sides are pitted against foreign counterparts.

It all starts tonight with two matches that can raise and answer questions about the strengths of the top teams in the country and with Celtic in Rennes and Rangers hosting Feyenoord there are points to prove against capable opposition.

Both sides have once again come through an arduous campaign to reach the group stage. Celtic started the summer in the elite competition but bounced back from the disappointment of exiting at the hands of CFR Cluj to reach the Europa League in some style. Rangers won a battle of wills with Legia Warsaw thanks to a single, decisive, and late, goal in what was a clear example of their year-on-year improvement.

Now, with that drama consigned to a footnote in the story of their seasons, the Glasgow rivals embark on the next immediate challenge: three points on offer to start a journey to the knockout stage but also an opportunity to lay down a marker for the rest of the group games.

Celtic start with arguably the most intriguing of their games. While Lazio is 'the glamour tie' and Cluj is 'the revenge game', Rennes is perhaps best described as 'the measure' for Celtic.

After the Cluj defeat, much of social media chat centred on whether Celtic were a Champions League club or a Europa League club. The simple answer would be that if you're a Champions League club then you don't have to ask, but the question draws a line amongst those below the top level that shouldn't really exist.

Rennes wouldn't be on anyone's list of Champions League-level clubs but last year they made a run to the last 16 of the secondary competition. They caught the eye in a 6-4 aggregate win over Real Betis and a 3-1 home beating of Arsenal. This season they already have a win over PSG ticked off as proof of potency.

So for Celtic, a real test awaits. In the wider picture, it's an opportunity to show that the Cluj setback was a blip, as performances before and after go some way to suggesting. But with Lazio firm favourites to top the group it's a battle to show who the second power in the section is.

Neil Lennon made a point of saying the French side have a style his team aren't used to facing. His Rennes counterpart Julien Stephan highlighted three Scottish internationals as examples of Celtic's technical quality, marking Callum McGregor, Ryan Christie and James Forrest as ones to watch. It's all set up for a fascinating encounter.

Back in Glasgow, Rangers start with the visit of Feyenoord. Where Rennes have the danger without the glamour, the Rotterdam side have a well-established name but not the form or players that made them a fearsome side in years gone by.

With Rangers in pot four and Feyenoord among the third seeds, the match at Ibrox is theoretically the most straightforward of the tasks awaiting Steven Gerrard's players in Group G. Handed a formidable draw, with Porto and Young Boys making up the quartet, there are no easy games, though some carry more expectation than others.

Gerrard stated as much in his pre-match media conference, saying the home games carried extra weight for his side, but was also confident his squad was more prepared for European competition than last year.

Having downed Legia, there's reason to believe Rangers can give a good account of themselves against Jaap Stam's Feyenoord. The bigger picture may have some Rangers fans thinking that breaking Celtic's stranglehold on domestic trophies is the priority, with Europe a (lucrative) bonus, but Gerrard was insistent in his belief he has the players to have "a good shot" at beating the odds and escaping the group.

That conviction isn't built on a projected series of results that includes a home defeat to the third seeds. Rangers have to take the game to the visitors and with Feyenoord's own ambitions dependent on accounting for the Scottish side before the dangers ahead, there's every chance opening night caginess gives way to something more cut-throat.

The start of the serious competition also gives the chance for evaluating the summer signings on the stage they were recruited for. Celtic's Boli Bolingoli, Christopher Jullien and Hatem Abd Elhamed will look to prove  they can provide the defensive bedrock for a run in the competition. And after slotting into the attack and providing a debut assist, Mohamed Elyounoussi could be making his case to become a key player.

Rangers fulfilled Gerrard's request to have two players seriously competing for every position this season and he will have big decisions to make when he plays his strongest hand on Thursday. Statement signing Ryan Kent is ruled out through injury, as is Jordan Jones, so Brandon Barker could get his chance to shine. Jamie Murphy's return to the first team could be escalated with two players out.

It's round one of six before Christmas but if there's one thing fans of Scottish clubs know it's that there's no room for error in Europe. By close of play on Thursday Scotland's representatives could be looking ahead with optimism to a series that can swell the coffers and raise the reputation but both know they won't get a second chance to make a first impression.