Despite that, bundesliga.com picks out five reasons the Turkish title-holders should still be very afraid of being steamrollered again by the Bavarian juggernaut in Wednesday's second leg in Istanbul.
A victory tonight would be a record-breaking 11th consecutive #UCL win for Jupp #Heynckes 👊— Bundesliga English (@Bundesliga_EN) 14 March 2018
Build-up to @FCBayernEN's last 16 second leg vs. Besiktas 👉 https://t.co/nT2N3Te8LB #BJKFCB pic.twitter.com/UdHMTTzEt7
1) Ruthless and relentless
You're five goals up, a second leg to play, but you're virtually through. What would you do? Take it easy, right? Sit back and cruise through the 90 minutes? Not Bayern. "We want to win every game. Also in Istanbul. We're going there to do our job well and go into the quarter-finals with another win," midfielder Arturo Vidal explained.
Any Besiktas fan hoping that is just pre-match bravado only has to look at last season…if they dare. Five-one up against Arsenal after the Last 16 first leg in Munich — sound familiar? — Bayern repeated the dose in a relentlessly ruthless performance to finish with a 10-2 aggregate win. Scared yet?
2) James is back
Great news for Bayern is bad news for Besiktas. James Rodriguez, who was forced off just before the break in the first leg with a calf problem, is fit again. The Colombia international has shown sizzling form in the Bundesliga since arriving from Real Madrid in the summer, and though he has yet to find the net in the UEFA Champions League, it is surely only a matter of time before he cuts loose in the competition he believes his club can win.
Watch: All of James' Bundesliga goals and assists!
3) The Lewandowski factor
Robert Lewandowski may be the deadliest striker in world football at the moment – with 31 goals in 34 competitive outings so far this season — and his confidence will only have been enhanced by him bringing up his Bundesliga century for Bayern at in the weekend romp against Hamburg.
The Poland international netted a hat-trick on Matchday 26, has scored four times in his last three Champions League games, including twice in the first leg, and netted 11 times in nine competitive outings in 2018. Need we go on? No, thought not.
4) Besiktas' Bundesliga angst
By defeating RB Leipzig in the group stage this season, Besiktas managed to break their decades-long duck against Bundesliga teams in European competition. Ever since they met Borussia Dortmund in the first round of the 1989/90 UEFA Cup Winner's Cup, marking their first official match against German opposition, they had not been able win a single encounter with a Bundesliga side, losing to Leverkusen in the 2006/07 UEFA Cup and drawing and losing to Wolfsburg in the 2009/10 Champions League group stage.
They also lost twice in the 1997/98 group stage. The German club's name? Bayern Munich. Mario Basler scored in the first of those ties; Carsten Jancker in the second. Alongside them on the scoresheet both days was Thomas Helmer – the centre-back who retired with 46 goals to his name, 24 of them for Bayern.
5) Inspire, not intimidate
Besiktas' Vodafone Park is renowned for its boiling-point atmosphere on matchdays, but Bayern are unlikely to be intimidated with Heynckes' squad well used to big European matches. "We have enough experience in the team to not be overawed," said Niklas Süle, one of the few members of the Bundesliga leader's squad not to be well into double figures in UEFA Champions League appearances. "We won’t let ourselves get carried away."
Thomas Müller, who will play his 95th game in the competition, even claimed post-match that Bayern are "looking forward" to the hostile welcome they will get, while Franck Ribery, who has first-hand experience following his time at Galatasaray, said with a smile, "It'll be a great atmosphere."