Jannik Sinner’s Wimbledon challenge has been narrowed down to one identified problem, adding uncertainty to his campaign before the grass-court Grand Slam. The concern matters because he arrives as the world’s top player, but Roland Garros exposed cracks after his shock second-round exit from a two-sets-and-a-break lead. If that issue carries over to Wimbledon, it could blunt his title chances at the tournament that starts the next stage of the season. The timing is especially important because this is the first major after a major setback in Paris.