Cilic still has plenty left in the tank

Marin Cilic is ranked No. 19 in the world

It has been four and a half years since Marin Cilic broke into the top 10 on the ATP, and his run in the top 10 lasted just nine weeks only to never return. So it is easy to forget that the Croat is only 25-years old - two years younger than the average player in the top 100. Even four and a half years removed from his career-high ranking, Cilic still hasn't reached his peak yet. 

Last year, Cilic was suspended for nine months from tennis after testing positive nikethamide. His suspension was eventually reduced to four months after an appeal, allowing Cilic to return to the tour at the start of 2014.

The Croat rejoined the tour with a ranking of 37 and a new coach. Goran Ivanisevic, a fellow Croat and former world No. 2, joined Cilic's team, looking to help him return to the top 10 after four years. Ivanisevic, who is the only player in tennis history to have struck over 10,000 aces, made an immediate impact on Cilic's game - Cilic was serving like his coach.

After years of tossing the ball behind his head and bending his back to reach the toss for a simple kick serve, Cilic began tossing the ball out in front of him and hitting it much flatter. And the difference showed up in the stats immediately.

Cilic averaged six aces per 10 service games in his career going into the 2014 season, but in 2014, that number is up from six to nine. He has seen similar increases in percentage of first serves made and won, allowing him to hold serve 85% of the time. In March, Cilic faced world No. 2 Novak Djokovic, who is known for his ability to get serves back in play, but Cilic still fired 13 aces in 12 service games.

His serve has improved so much that even though he has been breaking serve at his lowest rate since 2008, he is still seeing some of his best results in tournaments.

Cilic reached the final in Delray Beach without 
dropping a set and then beat
Kevin Anderson 7-6(6), 6-7(7), 6-4 in the final.

In February, Cilic won a pair of hard court titles and reached the final of Rotterdam. The final in Rotterdam was just the third time in his career that he reached the final of a 500-point event. That, to go along with two titles in one month, something he had only done three times in an entire season.

Cilic has continued to post solid results in 2014, reaching the round of 16 at consecutive North American hard court Masters events in the past two weeks. He also reached the semifinals in Umag and quarterfinals in Barcelona.

The one stumbling block for Cilic in 2014 has been Djokovic. Despite winning the first set against the Serb 6-1 in Indian Wells, Djokovic came roaring back to claim the match. The pair were drawn to meet again in the round of 32 at Roland Garros, where again Cilic took a set, but Djokovic took the match.

Cilic defeated world No. 6 Tomas Berdych en route to his
first career quarterfinal at Wimbledon this year.

At Wimbledon, Cilic reached his first grand slam quarterfinal since the 2012 US Open. And once again, it was Djokovic on the other side of the net. After splitting the first two sets, Cilic won the tightly contested third set in a tiebreaker, 7-4. However, Cilic's serve wilted away in the final two sets, getting broken four times, ending his run at Wimbledon and his chance to reach just a second major semifinal.

Cilic is now ranked No. 19 in the world, but has zero points left to defend in 2014 with some of his favorite events left on the calendar. The rest of the year is nothing but hard courts, where Cilic has won 77% of his matches this season. And many of those hard court events are indoors, where the Croat has won 86% of his matches in 2014.

Cilic is currently No. 13 in the Race Rankings, trailing No. 8 Andy Murray by less than 800 points. With his favorite part of the season left, Cilic could make a run for the top eight in the Race Rankings and a spot in the year-end finals.