Novak Djokovic and Big Four together again

There is once again a familiar look to the ATP rankings, with the Big Four back in the first four positions for the first time in quite a while. Various injuries, off-court happenings and time off have seen Roger Federer, Rafael Nadal and Andy Murray all fall down the ranks sometime during the previous couple of seasons, though Novak Djokovic has been a steady presence despite some fluctuations in form.

Following the Australian Open, however, the four are as before. Now they must look to stay there, holding off an increasing number of challengers. Here's how their campaigns are going.

Novak Djokovic

The Serb has not only been the most consistently ranking member of the Big Four, he is now dominating again, having just won his fifth Australian Open and eighth Grand Slam. It has become almost a regular event to see him sweep through the indoor season and pick up again on the hard courts, something he is doing once again. He is scheduled to return to the court at Dubai in two weeks and then is expected to play Davis Cup and defend titles in Indian Wells and Miami.

The only lingering issue from his Aussie victory was the apparent return of some fatigue problems. The 27-year-old seemed barely able to walk at times during his semifinal against Stan Wawrinka and final against Murray, though it didn't prevent him from winning both those matches. Still, it's something that plagued him during his rise up the ranks.

At least he's kept away from the heat since the tournament.

Roger Federer

Though winning fewer titles, Federer was even more consistent during the previous season than No. 1-ranked Djokovic, so it was a surprise to see him fall to Andreas Seppi at the Australian Open. But he was coming in off a busy stretch, playing a full indoor season that including reaching the championship match of the Tour Finals (before withdrawing, citing injury) and winning the coveted Davis Cup title. He also made appearances in the International Premier League and an exhibition for his charity. Federer started off 2015 by winning Brisbane.

Federer wouldn't attribute his early defeat at the Aussie Open to fatigue but did say he was now going to take a proper break. Federer also returns in Dubai as the defending champion. He is still deciding whether he will play Davis Cup in an attempt to keep the trophy Switzerland won in his most significant victory of the season.

Rafael Nadal

Unlike the others, Nadal's challenge coming in was too few matches, with the No. 3 hardly playing during the second half of 2014 and then getting just two or three matches before the Australian Open. He did spend a lot of time on court in Oz, including going five sets against Tim Smyczek in the second round, but the No. 3 then got pummeled by Tomas Berdych in their quarterfinal bout.

The Spaniard is going back to basics as he attempts to regain some consistency, returning to his favorite surface to play clay-court events in Rio and Buenos Aires. He told local television that he had been training in Mallorca and is now looking for "confidence and rhythm," not just for these tournaments, but in a bid to resume his dominance on European clay, and especially the French Open.

Andy Murray

Reaching the Australian Open final put Murray back at No. 4 in the rankings, but more importantly, it signaled his return to Grand Slam contention following back surgery, an extended comeback and changes to his team. He produced striking tennis in defeating Berdych in the semifinals but admitted to being affected by Djokovic's apparent fatigue in the final and appeared to almost question the legitimacy of the Serb’s behavior. Either way, he let Djokovic run away with the match, which meant Murray left the tournament with some positives and negatives: His game is back, but there are mental question marks.

The 27-year-old has been the first of the Big Four back on court, playing this week at Rotterdam. But first he had to explain his remarks following the final, saying his reaction was played up and seemed "bigger than what it was."

Murray went on to say: "If Novak feels he has something to explain, I’d be pleased to speak with him. But I don’t feel he really needs to explain anything."

Murray will also play the two hard-court Masters events next, followed (reportedly) by his wedding to Kim Sears, his longtime girlfriend, at a Scottish hotel owned by Murray.

The Big Four will be spread wide apart during these next few weeks, playing indoors, clay and hard courts in far-flung locations, but at least in the rankings, they are once more together.