Not content with sending the holders packing from the DFB Cup with an astounding 5-0 win earlier in the campaign, the Foals came away from the Allianz Arena on Friday night with one more memorable result, downing their rivals from Bavaria by 2-1 in a Matchday 18 thriller.
Florian Neuhaus and the outstanding Stefan Lainer were the goalscorers as Adi Hütter's men responded to going behind to Robert Lewandowski's opener, while Swiss shot-stopper Sommer made several crucial interventions to deny Lewandowski, Jamal Musiala and Serge Gnabry time and again.
"I'm overjoyed that we managed to keep a tight lead over time," the Gladbach custodian - who is approaching 250 Bundesliga appearances for Borussia - told the club's website following his team's sixth win of the season.
"Against Hoffenheim (1-1 on Matchday 17) we conceded a stoppage-time equaliser and it would have been a shame had that happened here (against Bayern) too," the 33-year-old continued.
The visitors held on to collect maximum points away from home for only the second time this season, adding three more to the point they picked up in the opening day 1-1 draw against Julian Nagelsmann's side.
"Bayern put a lot of pressure on in the second half and in one situation or another we were certainly a bit lucky, but we are very happy that we collected three points," Gladbach's No.1 explained. "We won and that helps us a lot; but now we have to keep going for the next few weeks and go into the next games with just as much courage, intensity and conviction."
Courage, intensity and conviction have become watchwords for the Swiss international, capped 72 times since making his senior Switzerland bow back in 2012. The Lake Geneva local was recently names Swiss Man of the Year, the prestigious annual prize handed out by publication Le Matin Dimanche.
Several outstanding displays by Sommer helped to propel Switzerland to the quarter-finals of last summer's rescheduled EURO 2020. Indeed, a stand-out moment for the 'keeper came when he saved a Kylian Mbappé spot kick in the Round of 16 shootout that eliminated tournament favourites France.
Ever present for Gladbach in Germany's top flight so far this season, Sommer is showing no signs of slowing down and is eager to keep facing the world's best strikers, like Lewandowski, who was ultimately denied one more Bundesliga double under the Friday night lights.
"You have to be really concentrated against (these forwards) because they're very clever, they make great runs and are good finishers, so you always have to be ready and be something of a perfectionist when it comes to positioning, speed and one-on-ones," the goalkeeper previously told bundesliga.com, adding, "It's a great challenge against these players."
High praise for the Swiss custodian has come from far and wide, with current Borussia Dortmund coach and former Gladbach tactician, Marco Rose, perhaps best summing up his former goalkeeper.
"Yann works hard every day to stay at the same level or even push further forward in some areas," the coach said. "He's an absolute role model. Yann is one of the best goalkeepers in Europe."
All in all, it's been a satisfying end to the week for the Bundesliga's Man of the Matchday, Yann Sommer.