Serena Williams
Serena Williams was taken aback by such a partisan crowd at Centre CourtReuters

World number one Serena Williams got the biggest scare in her journey at Wimbledon so far this year, after she somehow survived an upset against British No. 1 Heather Watson in the third round.

At one moment, Watson served for the match at 5-4 in the deciding set, and it looked like the grass-court Grand Slam was heading for another big shock. However, the mental toughness of the five-time Wimbledon champion prevailed over the 23-year-old's gutsy game and Serena recovered to win 6-2, 4-6, 7-5 in two hours and 15 minutes.

Following the match, Serena, 33, admitted she thought she was going to lose to the world No. 59.

"I honestly didn't think I was going to win," Serena said.

"How I pulled through I really don't know. I was thinking I would be hanging around to watch Venus play. I couldn't keep up with her. I thought maybe it just wasn't my day. I should have won the second set and I didn't. This was a match I think I would have lost last year or the year before."

The American, who will now meet her sister Venus in the fourth round, also commented that she battled a very one-sided crowd, and getting booed was something she never experienced before at Wimbledon.

"I don't think I've ever played the crowd here like that. They were really vocal – in between points, during points... I've never heard boos here, that was new for me," added Serena. "They were rooting for their champion. You can't blame them – I would be too."

Watson, who turned pro in 2010 - after she won the US Open girls' title in 2009 - had the best match of her career so far, as she walked off to a standing ovation at Centre Court.

However, she regretted the fact that she lost the match, despite being so close to winning it.

"No, I wouldn't call losing the greatest day of my career," Watson said.

"I was two points away so I'm pretty disappointed. Even now I just wish I could go back and play one point different to see if it would have changed things. It was a tough, tough ask. I was super, super close. That's what hurts the most."

Her performance attracted lots of praise from the social media and men's World No. 3 and fellow Brit Andy Murray was one of them:

Former England cricket team captain Kevin Pietersen also echoed the same. He wrote - "Heather Watson - quite brilliant! Unreal fitness & determination! But, Serena - incredible mental toughness! #Wimbledon"

Even Watson posted a tweet at the end of the day saying that she we would be back. "BEST ATMOSPHERE EVER... Honestly so blessed. Thank you everyone!! Serena proved why she is the best today... I'll be back tho I promise", she tweeted.