Bangladesh, ranked 187 in the world, lost 0-1 to Afghanistan in Dushanbe, Tajikistan in their World Cup qualifying opener on September 10, the same day India held reigning Asian champions Qatar to a famous 0-0 draw in Doha.
"It will be a very tough challenge as India are ranked 83 place above us, and a long way ahead of us with domestic football and facilities available," Day told from Dhaka.
Bangladesh take on Qatar at home on October 10 before locking horns with neighbours India five days later. They are at the foot of the five-team Group E at present. India find themselves in fourth position with one point from two matches. They lost 1-2 to Oman at home.
The eight group winners and four best runners-up will advance to the third round of Asian qualifying for Qatar 2022.
"We are preparing now with the players and have started our camp last week," said the 40-year old Brit, who played for Arsenal briefly.
Asked about the Indian players they are wary of, unsurprisingly Day said captain and record goalscorer Sunil Chhetri is Bangladesh's main threat.
"There is a few players we need to be aware of but Chhetri is the main goal scoring threat."
Bangladesh can expect to find support in Kolkata owing to proximity between the two states, West Bengal and Dhaka, and familiarity in terms of language and culture.
"I am hoping we can take a huge Bangladesh following to help the boys in this tough fixture," Day said.
On Bangladesh football, he added: "Most of our squad is under 23, so going forward this World Cup this will give them a fantastic experience to use.
"We need to improve our professional league and structure of our clubs to get the young players developing and into national team."
Abahani Limited Dhaka performed brilliantly in the AFC Cup recently.
As far as the 104-ranked Indian team under Croatian coach Igor Stimac is concerned, all players are currently in pre-season training with the clubs ahead of the Indian Super League which starts from October 20.
( With inputs from IANS )