Can Serena Williams be a Champion and Mom?

The tennis world is abuzz with speculation over the future of Serena Williams. In an already extraordinary week in which the 23 Grand Slam title-owning champion was projected to reclaim the World No. 1 without having played an event since this year’s Australian Open, Williams, in a cheeky snapchat post, announced that she was expecting.

If current reports are accurate, Williams is 20 weeks along this week, which means she was 8 weeks pregnant at the time she won the 2017 Australian Open, joining Margaret Court and Evonne Goolagong as some of the few women who have been at the top of professional tennis while with child.

Williams now also adds to a growing list of anticipated comebacks among top players that includes Maria Sharapova, Victoria Azarenka, and Petra Kvitova. Sharapova, who has been away from the game for 15 months serving a drug ban, will be the first to return when she plays at the Stuttgart Grand Prix next week. Kvitova, who has been recovering from a shocking knife attack at the start of the year, has had a rapid recovery and is currently on the entry list for the 2017 French Open. Azarenka, whose situation is closest to Williams', became a mother in 2016 and is expected to return to the tour this summer.

As ages at the top of the women’s and men’s games have been trending upward over the past decade, we shouldn’t be surprised that more players are having families while trying to maintain their competitive career. Even with minimal time off, we can guess that Williams would be 36 and a half years old or older if she were to comeback to the sport, making her one of the oldest singles player in recent history.

Her sister, Venus Williams, played Serena in this year’s Australian Open final at the age of 36. But Venus has never had a child. What are the odds that Serena Williams could overcome the challenges of age, childbirth and child-reading to make a successful return as a mother?

Kim Clijsters has been the only women since Evonne Goolagong to win a Grand Slam title after having a child. That stat would suggest that a comeback like Clijsters' would take something approaching a miracle. But Williams has been one of the most miraculous players in the sport— winner of the most Majors in the Open Era and the highest-earning female athlete of all time—so normal odds might mean little in her case.

With so few historical examples that can be compared to Williams, can we look at her own playing history for signs that could support her chance of a strong return?

Even with the most rigorous training, we can expect that being a year older and having gone through childbirth will mean that Williams may never return to the physical shape she has been at in recent years. But this need not diminish her match win rate if she finds strategies to compensate for any decline in her physical capacity.

Playing more efficiently by keeping points short and not wasting opportunities would be one such strategy. And, if we look at Williams' stroke production from 2015 to 2017 at the Australian Open, it appears she has already put this strategy into practice. The chart below shows the cumulative strokes hit, adding up all serves and groundstrokes, in each match of the AOs from 2015 to 2017, 2016 the only year when she didn’t win the title, losing in the final to Angelique Kerber.

The dashed lines show what the cumulative stroke production would be for 25% of players with the lowest production (below) and the 25% with the highest production (above). We can see Serena has had one of the lowest production rates in each year but has managed to decrease her rate even further over time.

In 2015, Williams' average shots per match was 215 but was down to 174 this year, a near 20% reduction. By the final match, that change translated into a 24% reduction in the cumulative shots in the event between those years.

Surprisingly, these efficiency gains have come at a time when she has lost some edge on her first serve. At the same time, she has become more aggressive on her second serve, which could explain how she has still found a way to increase her efficiency overall. Between 2015 and 2017, Serena dropped 5 kph on first serves on average but gained 3 kph on second serves.

What else could contribute to her increasing efficiency?

Attacking on the serve return is another factor we have to consider. Williams is notorious for stepping inside the baseline on the return. Has she gotten even more aggressive with her return position in recent years?

The charts below summarise Williams' serve return position on first serve. For simplicity, only 2015 and 2017 are shown. In general, we see that Williams was further inside the baseline in 2017 compared to 2015, coming in 13 cm on average across all matches. It was 16 cm in the first four rounds, suggesting that Williams was even more aggressive in her stance in the earlier rounds.

With motherhood, Serena Williams will face a whole new set of joys as well as challenges. How all of these changes will affect her ability to return to the sport is difficult to project, especially at this early stage. If the recent past in her performance can shed any light on the question, it does show us that she has been able to adapt her game to a more energy-conserving style of play while maintaining her match dominance. That could prove to be a winning formula if, as a mother, Williams make a return to the professional game.