The dominating narrative of the 2018 World Cup so far has no doubt been that of the favourites struggling, and the smaller nations punching above their weight - a narrative that was no better epitomised than in the opening fixtures of these two sides.
Japan were probably the least fancied side in this group before they faced Colombia, who were widely expected to repeat their 2014 showing and win Group H, but that didn't stop Shinji Kagawa and Yuya Osako striking to upset the apple cart and help Japan to a 2-1 win.
Senegal, meanwhile, who had only won one previous World Cup match in their history, were able to upset a Robert Lewandowski-led Poland, and in doing so blew the group that was thought to be the most open in the tournament even more so.
With this in mind, both sides, neither of which were fancied before the tournament kicked off, have a chance to all but secure qualification on the second day, which will make this one one of the 2018 World Cup's most interesting match-ups so far.
Japan weren't fancied going in given their sketchy immediate form. Warm-up friendlies featured defeats to Ukraine and Ghana and a draw with Mali, which understandably left many uninspired and unexpected of Akira Nishino's side.
Despite this, though, they looked a rejuvenated side in their opening day victory over Colombia, as they were organised, resilient and had the quality in the chamber to get the job done.
Senegal, meanwhile, have been a hard side to analyse. They followed up a disastrous 5-0 African Cup of Nations exit to Guinea with a fantastic World Cup qualifying campaign, going undefeated in the final stage.
They went on to draw three friendlies they should have won, before narrowly losing to Croatia and then beating South Korea prior to their shock Group H victory over Poland.
World Cup Highlights
Picking Senegal's World Cup highlights wasn't exactly an arduous task. Prior to 2018, they've only been to one World Cup, in 2002, when they famously finished second in the proverbial 'Group of Death' ahead of France and Uruguay, going on to put Sweden out in the last 16 before eventually bowing out to Turkey in the quarter finals after extra time.
Japan's most famous World Cup showing came at the same tournament, winning their group ahead of Belgium before losing in the last 16 to the same side who would eventually end Senegal's dream in the quarter-finals.
Japan have a full 23 to choose from heading into this one, but may opt to start with the talismanic Keisuke Honda, who crossed for the winner after being left out of the starting XI against Colombia due to poor form for AC Milan.
Senegal, meanwhile, are expected to start with much the same line-up that beat Poland last week.
Japan (4-2-3-1): Kawashima; Nagatomo, Shoji, Yoshida, Sakai; Hasebi, Shibasaki; Inui, Kagawa, Honda; Okazaki
Senegal (4-4-2): K N'Diaye; Sabaly, Koulibaly, Sane, Wague; Mane, A N'diaye, Gueye, Sarr; Niang, Diouf
This one is about as open a game as you can expect to see at a World Cup. Neither side has anything to lose having already registered a victory in the opening day, however Japan have the slight edge for qualification having already played, and defeated, Colombia.
That said, though, Senegal look to have a bit of quality and attacking flair in their ranks that Japan just don't possess. The likes of Sadio Mane and Mbaye Niang, if utilised properly, could prove deadly to Japan, and help Senegal to the last 16 for the second time in two World Cup appearances.
Prediction: Japan 1-2 Senegal