That was a collective shiver down the spine felt around the WTA last week. Serena Williams destroyed the field at the Family Circle Open, again indicating she can dominate women's tennis when she is healthy, and apparently she has never felt better.
She conceded only one game to Lucie Safarova in a 6-0, 6-1 final at the event in South Carolina, and routed Samantha Stosur, the world No 5, in a 6-1, 6-1 semi-final, prompting the Australian to say: "She was way too good."
Her serve was not broken in 25 games. She leads the WTA in aces with 108, despite playing only four tournaments in 2012. In the final, the speed of her serve hit 186kph.
She was so enthused with her form that she suggested she might have hit a zenith, at age 30.
"I can't say that I've played this consistently or well," she said after securing her 40th WTA championship, third-most (behind sister Venus and Kim Clijsters) among active players.
"I've always said that when I play really well I'm very difficult to beat."
Injury and illness, including a life-threatening pulmonary embolism, sidelined her for nearly a year ahead of Wimbledon.
She made the last 16 there, then won at Stanford and Toronto and reached the US Open final.
She took off the rest of 2011, and her bid at the Australian Open in January was short-circuited by an ankle injury.
She returned in time for the Sony Ericcson Open, where she reached the quarter-finals, then won at Charleston.
"I feel like I'm finally back," she said. "I can be more serious about everything I do. The near-death experience changed my whole perspective. I'm having more fun because I almost never made it back."
Her short-term goal is winning the French Open. From her 13 slam championships, she has only one title at Roland Garros, in 2002, but the victory on the clay at Charleston suggests she might be ready for a deep run in Paris, which starts on May 27
A healthy Serena brings with her a level of confidence perhaps unmatched in tennis, understandable, given her status as the strongest player on the tour.
When considering the top-ranked players, she said: "I never say, 'Oh, my goodness, I can't beat them!' When I do that it's time for a new career."