The Mets long have come in on the wrong side of their rivalry with the Braves, and now Atlanta might be making a serious run at one of the Mets' top free agent targets - closer Billy Wagner. Two baseball executives said yesterday that Braves GM John Schuerholz was planning to meet with Wagner's agent, Bean Stringfellow, this week. Wagner had acknowledged interest by the Braves and Red Sox when he met with New York-area reporters following a visit here last week, but noted they "have other things on their plate right now." However, a scheduled meeting is a sign that the Braves' pursuit could heat up. As one baseball executive said yesterday, "Schuerholz seems to do something every year."