ATLANTA — Adrian Morejon, the set-up man who has emerged as the hardest-throwing left-hander in baseball, could end up as the best reliever moved by the Aug. 3 trade deadline, even as the San Diego Padres continue to take a wait-and-see approach amid a summer of poor overall performance.Despite the speculation swirling around Mason Miller, the club-controlled All-Star seems likely to remain with the Padres, according to people familiar with the team’s thinking who were not authorized to speak publicly. The Boston Red Sox have made a historic surge into the American League wild-card race, greatly reducing the chances of a trade involving Aroldis Chapman. Another elite alternative, Josh Hader, has full no-trade protection as part of his five-year, $95 million deal with the Houston Astros, who hope to buy at the deadline, anyway.If all three closers stay put — no certainty this time of year — that could leave Morejon as the top bullpen prize for any number of contenders.Morejon, a 27-year-old pending free agent, has pitched better than his 3.33 ERA would suggest. The underlying numbers include a 2.55 expected ERA, a 99.2 mph average fastball velocity, and Morejon’s place at or near the top of the major-league leaderboards for Stuff+ and Pitching+. This winter, when he will become arguably the most coveted reliever on the open market, he should command contract offers well beyond San Diego’s comfort level.Who are the top prospects in baseball right now? Keith LawHowever, deciding whether to move Morejon in exchange for controllable talent might not be so simple for the Padres and A.J. Preller, the club’s notoriously aggressive general manager.Thursday’s 6-5 loss to the Atlanta Braves dropped the Padres to 50-53. Their FanGraphs-calculated playoff odds fell to a mere 7.1 percent. San Diego has opened the second half by going 2-5, showing real signs of life on offense but failing to overcome a glaring lack of starting pitching.Still, Preller has continued to signal to rival executives that he hopes to be in a position to buy at the deadline, team and league sources told The Athletic. Most of those sources believe the Padres intend to wait until very close to the deadline to make significant decisions — whether they involve buying, selling or a combination of both.