The simultaneous nature of online auctions changes the horizon a bidder faces. A seller then has to make strategic and/or operational changes in order to adapt. In this study, a three-stage game model is constructed to analyse seller reserve price setting decision in online auctions. The decision of whether a seller should set a reserve price is shown to be a function of the covariance (between expected seller profits and expected rivals) and the expected number of bidders, where the covariance term is jointly determined by possible actions of other sellers.