The 2015 quarter-finalists shocked South Africa in their tournament opener but defeats by New Zealand and England brought them down to earth.
"It's not easy, especially the conditions," the all-rounder told reporters ahead of their match against a Sri Lankan side who have been far from convincing themselves.
"Obviously we'd love to see ourselves in the semis, but again, the calculation is right now a lot, lot difficult.
"If we could manage to win one of those matches against New Zealand or England, it could have been a lot easier.
"At the moment, it looks very difficult but I say it's possible, it's very much possible. We have to make sure that we come back to the winning track and then have a look what happens next."
Sri Lanka were thumped by New Zealand but the 1996 champions edged out Afghanistan and claimed a point from their washed out match against 1992 winners Pakistan. They lie one point ahead of Bangladesh in the 10-team standings.
Mashrafe felt the two-wicket loss against New Zealand has intensified pressure on the team but was optimistic they would respond positively.
"After beating South Africa, our confidence level was high that we can beat New Zealand but we couldn't," he said.
"Pressure will be there in every match but at the same time I have to say that we have to cope with that pressure and make sure we deliver.
"A few things can go out of plan but we have to make sure that at the end of the day, we are on the winning side."
(Reporting by Amlan Chakraborty in London; editing by Pritha Sarkar)
