Neil Harris believes the seasons of a number of Championship clubs will be defined over the Easter period.
Harris' men are just four points off the Play-Off places after hitting a purple patch since the turn of the year and can close the gap further by prevailing over mid-table opposition this weekend.
The Lions will host Nottingham Forest at The Den on Good Friday before travelling to Ipswich Town three days later.
"We are in a fantastic position with eight games to go but the job's not done yet," Harris told millwallfc.co.uk. "It's a massive weekend for us.
"Is it make or break? Yes, it certainly is for a lot of teams and we are one of them. A good points total has us in the mix and we want to continue that good run of form that we've been in.
"We look forward to carrying momentum from our unbeaten run in the League. Forest are a big club and we need to impose ourselves on the game on Friday."
Seven players were recalled by their respective countries and the manager believes his players will benefit from the exposure to international football.
"All players are back in this week and they will be hungry," Harris added.
"It's always good when fixtures have been so intense and we have been going so well that you can give the players some time away. They need a break from the training ground and certainly a break from hearing my voice everyday.
"It's a bit of a strange period at this time of year where you don't see a lot of the lads for 13 days over the international break, but that's the football calendar. Everyone is back now and we will prepare for the remaining eight games."