Pietersen, who has just returned from three months out following a knee injury, was rested as England lost by five runs in the opener of the two-match series at The Oval on Tuesday.
However, the 32-year-old, who hit an unbeaten 177 for Surrey in the County Championship, is ready to go for the second match later this week.
"My role is to get him in and his role is to win the game," Morgan told Sky Sports News. "Kevin is a huge part of English cricket and has been for a long time. What he brings to the table probably very few people in the world can.
"He can take the game away from you at any stage and we saw during the week the way he performed, he takes a lot of pride in when he goes out there and bats.
"He looks in good form."
Thursday's match is also at The Oval and you can follow live updates here on Sports Mole from around 6pm.