What happened: Jannik Sinner is back on court at Wimbledon for his second match as he begins the defense of his title. His opening match left lingering questions about whether he has fully found his rhythm on grass. Each round now becomes another test of whether the world No. 1 can round into the form expected of a defending champion.

Why it matters: A title defense at Wimbledon carries outsized weight for the top-ranked player, where early-round stumbles can define a fortnight. Sinner's grass-court form is a central storyline of the tournament, and how he answers the doubts from his first match will shape expectations for the draw ahead. For a No. 1 seed, the margin between cruising and scrapping through early rounds often signals how deep a run becomes.

What to watch: Watch whether Sinner tightens his level as the match and tournament progress, and how his serve and movement hold up over best-of-five on grass.