Phelps, whose record 22 Olympic medals include 18 gold, caps his career with a fifth Games appearance in Rio. But just as he’s far from invulnerable at 31, so the United States could find itself hard-pressed to match their 2012 haul of 16 gold medals, nine silver and six bronze. Australia, in particular, are aiming to rebound from a shocking London Games — their first since 1976 without an individual gold. Australian coach Jacco Verhaeren, however, said the 2016 squad’s mission has nothing to do with atonement. “I don’t think we’re here to make up for any disappointment,” he said. “Nobody is busy with what happened or what might happen.”