Delhi captain Gautam Gambhir has been ruled out of Friday's IPL match against Chennai because of a hamstring injury.

"He is going for a scan to see how bad it is. Only after we assess him, we will know how long he will be out of the tournament. It's reasonably serious and he won't play tomorrow," assistant coach Eric Simmons told reporters on Thursday.

"We don't know how bad it is at this stage," he added.

In his absence, Dinesh Karthik will lead the side on Friday.

Gambhir pulled hamstring during Wednesday night's match against Mumbai.

Delhi will surely miss Gambhir but Simmons hoped a balanced Delhi side would take the field.

"It's an interesting situation now but we have a lot of options. Twenty20 is all about fielding a balanced side," he said.