Novak Djokovic has dominated this season, and a new crop of young stars have made breakthroughs. Other than that, it's been a less-than-stellar showing all around.

Here are our first-quarter men's grades:

No. 1 Novak Djokovic: A+

In a season that began with a string of controversy, Djokovic has been the standard-bearer of consistency. He practically swept the first quarter, winning Doha, the Australian Open, Indian Wells and Miami. His only loss came via retirement in Dubai because of an eye infection.

Though taking any issue with his performance would be mere quibbling, Djokovic did not finish the quarter looking as untouchable as he did in the beginning. In Miami, he had patches of double-faulting; he also suffered from a minor back injury and looked drained in the hot and humid conditions. Still, Djokovic kept winning and winning.

No. 2. Andy Murray: B

Murray could use some positive momentum. Playing the 2015 Davis Cup final in late November meant he didn't get much of an offseason. Further, his year began with an eventful Australian Open. Murray entered the event with the impending birth of his first child hanging over his head, and midway through the tourney, his father-in-law, Nigel Sears, collapsed in the stands.

Somehow, Murray reached the final, then immediately flew home for the birth. He made a winning return in the first round of this year's Davis Cup competition, but a few weeks later, his performance dipped, producing error-prone performances in second-round losses at both Indian Wells and Miami.

No. 3 Roger Federer: Incomplete

It seemed to be going well for Roger Federer until knee surgery derailed his schedule. AP Photo/Rafiq Maqbool

There aren't many firsts for Federer these days, but the 17-time Grand Slam champion underwent his first career surgery after the Australian Open, having injured his knee while, of all things, getting up in the morning to prepare a bath for his two daughters.

On the plus side, Federer's rehab went so well he decided to return ahead of schedule and play Miami, only to withdraw from the tournament with a stomach bug.

It all means he's played only two events this season, though it should be noted in those events, he reached the final of Brisbane and the semis in Melbourne.

No. 4 Stan Wawrinka: B

The two-time Grand Slam champion is ranked No. 4 but still hasn't been as consistent as the traditional Big Four. Wawrinka picked up two titles this season at Chennai and Dubai, but a surging Milos Raonic beat him in the Australian Open quarters. Wawrinka's recent form hasn't been great either, as he was upset in the fourth round at Indian Wells by David Goffin and dropped his opener in Miami.

No. 5 Rafael Nadal: C+

It says a lot about where Nadal is at the moment that two losses against Djokovic have been the highlights of the Spaniard's first quarter. He reached the final at Doha but was thumped by the No. 1. Nadal then had a much tighter meeting against Djokovic in the Indian Wells quarterfinal.

Other than that, Nadal has dropped matches he should have won, including a five-set defeat to Fernando Verdasco in the Aussie Open first round and three-set losses against Dominic Thiem and Pablo Cuevas in the South America swing. But most troubling was Nadal's retirement in the Miami opener because of an apparent heat illness.

No. 6 Kei Nishikori: B+

The 26-year-old from Japan played quite well the first three months of the season. Nishikori reached the quarterfinals of the Australian Open, won Memphis and made the Miami final. Whether he can parlay these performances into another Grand Slam final run is still the overwhelming question moving forward.

No. 7: Tomas Berdych: B-

The Czech has settled into the middle part of the top 10, rarely falling to those ranked below him but also not making as much of an impression on those ranked higher. However, recent losses to up-and-comers such as Raonic and Nick Kyrgios suggest Berdych might have to shake up his game to stay at the upper levels.

No. 8. David Ferrer: C+

An unmotivated Ferrer is as unheard of as an injured Federer. But that seems to be the reason the Spaniard withdrew from Indian Wells, possibly frustrated because he didn't pick up a single title during the South American swing, where he usually excels. Returning to Miami, Ferrer fell in a long three-setter to Lucas Pouille.

Biggest gainers

No. 12 Milos Raonic: He's played only four events, but trails only Djokovic in overall success. Notably, Raonic made the semis in Melbourne, the final at Indian Wells and the quarters in Miami.

No.13 David Goffin: He rode his Davis Cup confidence to an Australian Open quarterfinal and then the semifinals at Indian Wells and Miami, putting him on the edge of the top 10.

No. 14 Dominic Thiem: Two titles in South America and a tight match against Djokovic in Miami means the 22-year-old is rapidly rising.

No. 16 Gael Monfils: He has taken advantage of favorable draws, suggesting he's competing better. In Miami, he took down Grigor Dimitrov and lost a heart-breaking third-set tiebreaker against Nishikori in the quarterfinals.

No. 20 Nick Kyrgios: The 20-year-old won his first title and then made his first Masters semifinal, at Indian Wells. It looks like he is starting to consistently play up to his potential.

No. 26 Pablo Cuevas: A win against Nadal and a couple of clay titles has the veteran riding a wave of resurgence.

No. 45 Andrey Kuznetsov: He reached the fourth round of the Australian Open and has also won at least two matches in every tournament he's played.

No. 52 Alexander Zverev: The 18-year-old has made some good runs and been on the verge of victory against a couple of top players -- including Nadal. Next is actually getting those victories.