What's on her CV?
Carolina Marin is currently the top ranked player in women's badminton. She's left-handed, stands 172 cm tall, and is playing in her second Olympics. She's won the World Championships twice (2014 and 2015) and has been on top of the rankings for all but two weeks this year. She's the first player from Europe to reach the finals in the women's singles at the Olympics and holds the record for being the youngest European winner of the Worlds. She's been the standout player on the international circuit in the last two years and it would not be a surprise if she wins.
What's her game like?
Marin is one of the swiftest movers around the court, has a powerful smash and is particularly adept at playing cross court. Her unique advantage, though, is that she's lefthanded - the only left-handed player in the top 10; that helps her create difficult angles for her opponents. Marin cites Rafael Nadal as her favourite sportsperson and her game from the back of the court is very similar to Nadal's. She tends to be very aggressive and positive and is known to keep her cool in tricky situations.
What's her previous with Sindhu?
Marin currently has a 4-3 edge in her head-to-head encounters against Sindhu. They last met in the first round of Hong Kong Open last year in November, when Marin won 21-17, 21-9 in 35 minutes. Marin has won all her four matches against Sindhu without dropping a game and Sindhu has never crossed 17 points in any of those games. Sindhu's two wins over Marin have been in three sets; the last win over Marin came in the semi-finals of the Denmark Open in October 2015. Since the beginning of 2015, Marin has won as many as seven tournaments while Sindhu has won two.
How do the coaches stack up?
Marin is coached by Fernando Rivas, who's been the Spain coach since 2005. He has a degree in sports science and is known to let players make their own decisions. He doesn't talk much to Marin during games, in stark contrast to Sindhu's coach P Gopichand, who is very hands-on coach and known to make detailed plans and strategies for all his players. Rivas' influence can be clearly seen on Marin as she has the unique ability to alter her game in the middle of the match based on how her opponent is scoring, unlike Nozomi Okuhara and Wang Yihan, whom Sindhu defeated in the previous rounds.
How's Marin fared in Rio?
Marin has not been challenged at this Olympics so far; she is yet to drop a game. She has won 168 points and only conceded 97 points, which is a huge difference in a strong field. Sindhu, by contrast, has dropped a game and won 230 points and lost 166 points, albeit playing an extra match.
What's Sindhu's best bet against her?
Sindhu has mostly attacked her opponents' backhand in her matches so far and has made judicious use of the drop shot. Her best opportunity against Marin would lie in staying patient and extending the rallies and mixing the pace of the game as Marin mostly keeps a brisk tempo. Marin has a tendency to win and lose points in a bunch and it would be critical for Sindhu to not let Marin run away with the match.