The right-arm seamer picked up a left hamstring injury during training, later revealed to be a grade 1 tear, ruling him out of action for between three and four weeks.
Tamim does have previous international leadership experience, having skippered the Tigers in one Test in New Zealand in 2017 following an injury to then-captain Mushfiqur Rahim. This will however be his first time leading in ODIs.
The Bangladesh Cricket Board declined to name a replacement in the squad, which has already been announced. The sides will play three ODIs in Colombo, on 26, 28, and 31 July.