What’s the story?The 2018 Australian Open suffered two big casualties on Thursday morning as Andy Murray and Kei Nishikori both pulled out of the season’s opening Major. While Murray is still battling a persistent hip injury, Nishikori has failed to recover in time from a wrist injury.The official news of the double pull-outs was announced by the Australian Open on Twitter.Unfortunately @keinishikori has withdrawn from the #AusOpen.“The Aussie Open is my favorite Slam...it’s my ‘home’ Slam...and it hurts that I will miss this year.”All the best, Kei, see you next year ??— #AusOpen (@AustralianOpen) January 3, 2018Murray: “Sadly I won’t be playing in Melbourne this year, as I am not yet ready to compete. I’ll be flying home shortly to assess all the options.”Good luck for the rest of ‘18, @andy_murray, you’ll be missed! https://t.co/yzRIypFXM7— #AusOpen (@AustralianOpen) January 4, 2018In case you didn’t knowMurray has been a consistent performer at the Australian Open, where he has been a five-time runner-up. The former World No. 4 Nishikori too has fared well at the first Slam of the year and has reached the quarter-finals thrice. The heart of the matterThe three-time Slam champion Murray hasn't played a competitive match ever since his Wimbledon title defence came crashing at the hands of Sam Querrey in five sets in the quarter-finals last year. He was looking forward to beginning the new season at the Brisbane International, but after playing a few practice sets with top players the Scot didn't feel confident about his level and pulled out of the event.The former World No. 1 then apologized to fans in a long, emotional Instagram post, detailing about his recovery where he hinted that he might have to consider surgery if the rehab does not work out well.Nishikori hasn't been in action since the Montreal Masters in August, where he lost the opener to Gael Monfils. The former US Open runner-up too was scheduled to make his return at the Brisbane International but had to withdraw right before the event.What’s next?Murray will return home to assess all options in a bid to recover fully from his injury. As for Nishikori, he will continue with his rehab and will only join the Tour when he feels ready.Author’s takeThe new is indeed utterly disappointing for fans. That said, a player's health is of paramount importance. It is absolutely not wise to take a major risk right when the new season is beginning. Let us hope Murray and Nishikori can recover quickly and be back in action as soon as possible.