Manning aggravated an injury to his right ankle during the Broncos' 28-20 win over the San Diego Chargers last weekend, but an MRI scan yesterday showed no new damage to the sprain he initially picked up a month ago.
Del Rio revealed that Manning could be given some time off practice this week if required, but he is in no doubt that the 37-year-old would start Sunday's match.
"We did get good news that there was nothing additional, good results coming back. [Manning] will definitely play this week. So that's good news," Del Rio told reporters.
"He'll get an occasional day off here and there. We'll decide when that makes sense or not, we'll manage that as we get closer to Wednesday, Thursday.
"He'll definitely play this week. He's ready to roll, so that's definitely good news."
Sunday's showdown with Kansas City is a crucial match at the top of the AFC West, with the 9-0 Chiefs currently edging the 8-1 Broncos in the division.