[RKBUmp]

DP is an offensive position that can play defense, the Flex is a defensive positioin. The DP can play defense for any player other than the Flex without it being considered a substitution. If the DP does play defense for the Flex, the Flex has left the game, the lineup has dropped to 9 players and it counts as a subsitution for the Flex. The Flex can bat only for the DP, but if they do, it counts as a substitution for the DP and again the lineup has dropped from 10 to 9.

The lineup can change back and forth between 10 and 9 any number of times, however, the players in those positions are still only entitled to 1 reentry each.

In ASA ball the DP playing defense for anyone other than the flex doesnt have to be reported unless they playing for the pitcher or catcher. Then you would need to report them in order to use a courtesy runner if you so choose.