This time last year, Heather Watson's promising career appeared to be in sharp decline.
In 2012, the 22-year-old from Guernsey had become the first British woman since 1988 to win a WTA title and the first in a decade to reach the third round at Wimbledon.
But a diagnosis of glandular fever, which Watson says left her so tired she felt like "exploding", in April 2013 had a devastating effect on her form.
A two-month break proved insufficient to overcome the debilitating illness and, when Watson returned, the power and movement that had taken her into the world's top 40 had all but disappeared.
She lost in the first round of the French Open, Wimbledon and the US Open and slid outside the world's top 100.
Desperate for a remedy, Watson split from her long-term coach Mauricio Hadad and appointed Diego Veronelli, an Argentine who had enjoyed success in charge of his compatriot Paula Ormaechea and Joao Souza of Brazil.
The results have been spectacular. Playing with far greater aggression and purpose, Watson won the prestigious ITF title in Michigan in February and - following a two-month lay-off for shoulder surgery - the Prague Open in May.
At Eastbourne last week, she ousted Italy's Flavia Pennetta to record her first victory over a top-20 player, and in the first round at Wimbledon on Tuesday she lost just five games in sweeping aside Ajla Tomljanovic of Croatia, a player ranked seven places higher at 53 in the world.
On Thursday, Watson faces the biggest challenge of her career: a meeting with ninth seed Angelique Kerber for a place in the third round at the All England Club.
Here, former British number ones Anne Keothavong and Jo Durie, who are covering Wimbledon for the BBC, explain the reasons for Watson's resurgence and analyse how she can get the better of the in-form left-hander from Germany.
On the attack
Anne Keothavong: "It's great to see Heather back up there competing at the highest level again. I watched her against Pennetta and she played superb tennis. I think last year was a tough year for her. She probably came back too soon from glandular fever but she seems really happy right now.
"I think the key is her relationship with Veronelli. He seems like a great guy and they communicate very well with one another, which is vital to any player-coach relationship. You have to be able to speak openly and tell each other what you think.
"We know Heather is a very good mover and very athletic but she is certainly trying to play more aggressively now and it is paying off.
"She just needs to look at someone like Simona Halep and see how she has progressed in this last year by using her movement very aggressively."
Jo Durie: "Heather seems to be really enjoying her tennis. I think she panicked a bit about her ranking dropping at the end of last year, but this year she has started fresh and now she is back with a good, balanced mental attitude.
"I was very impressed with Heather in the first round because she had everything under control. As the match went on, whatever Tomljanovic tried to do, Heather had an answer.
|Fed Cup captain Judy Murray on Heather Watson|
|"Heather has been up in the top 40 before, she has beaten top players before, but now she has to do that on a consistent basis. That's about getting your head and body in the right place for much longer periods of time. I think she will have learned a lot from last year."|
"When the Croat tried to hit it a bit harder, Heather upped her pace and served beautifully as well. It's not just the speed of the serve but where she was placing them - it was all very precise.
"I think she knew she had to become more aggressive, but it was just a case of making the decision and then having the right person there to help her do it. She has great trust in her new coach and seems to be really enjoying trying to attack more.
"You have to accept maybe you will miss a few more shots but to live with these top women who hit the ball so hard, you have to attack."
How to curb Kerber
Keothavong: "Angelique Kerber lost to Laura Robson here in 2011 but that has spurred her on and we have seen her career rocketing since. She is a tough opponent, a player I faced many times and didn't have that much success against.
"She's a solid player off both wings and has a great forehand down the line, but her serve is something Heather can look to exploit. Her first serve is not the biggest and her second serve sits up quite a bit, so Heather needs to be ready to put it away.
"Although Kerber moves very well from side to side, she's not very comfortable coming to the front of the court. Heather needs to go out there with an aggressive mindset but also stay patient and really work the point.
|Angelique Kerber factfile|
|Born: 18/1/88 in Bremen, Germany; World ranking: 7; Turned pro: 2003; Career titles: 3; Grand slam best: Wimbledon semi-finals in 2012; Career win-loss: 387-218|
"You have got to think big, want big. She can't be satisfied with just winning a round or two at Grand Slams. She has to be thinking about winning and getting herself through into the second week."
Durie: "It a huge test for Heather but what a great match to have a go at. There's no pressure.
"Kerber is not going to hit her off the court so Heather should try to stay with her in points. The German can have her spells in matches where she gets frustrated with herself. Heather should go after the second serve, which she is capable of doing.
"She must be courageous and go for it. You have to believe you have a chance. Where better than on the grass of Wimbledon?"