Ace-maker Karlovic can still hang with the top dogs

— -- It is again time to hand out our year-end awards. Today, we look at the top men's unsung heroes of the year, but click here to check out the rest of our list.

Top men's unsung heroes

It's the "best of" season in tennis, when everyone gets to choose their top performers, top shots, top moments, top everythings. It's an enjoyable exercise and a nice journey through the just-completed year, but by definition it leaves out a lot.

After all, there are two forms of success -- the quantifiable kind, easily measured in title counts and rankings. Then there's the relative kind: how someone fared relative to their skills, personal history and expectations.

So let's acknowledge three players who didn't have anywhere near the kind of year that would land them on a "best of" or "most this or that" list. In fact, only one of them hit his career-high ranking this year. But all three have abundant reasons to feel proud of their performances in 2015.

Ivo Karlovic

Does any shot in tennis command more respect and resonate with a greater sense of authority and finality than the service ace? This year, Karlovic surpassed Goran Ivanisevic to become tennis's all-time ace-maker, popping out the unreturnables like a 6-foot-11 Pez dispenser.

Karlovic hit the record-setting 10,238th ace of his career at the China Open this fall. He banged it out during a 26-ace performance against Pablo Cuevas. Perhaps fittingly, Karlovic lost the match in two excruciating tie breakers. The tennis gods have a sense of humor, after all.

You know how Karlovic is: On a day when he's merely serving well, he beats most guys outside the top 30. On a day when he's serving and volleying well he can beat most guys outside the top 10. On a day when he's serving and volleying well and getting a few returns back into play he can beat anyone -- including Novak Djokovic.

In fact, Karlovic was the only player outside the year-end top five to beat Djokovic in 2015. It was no fluke, either. Karlovic is 3-1 against Djokovic, sweeping their hard-court meetings while losing their sole encounter on clay.

Rapidly closing on age 37, Karlovic is the oldest player in the ATP top 200. Currently No. 23, he's just nine ticks off his career-high ranking of No. 14, which he hit more than seven years ago. Karlovic has proved astonishingly durable. And he won a title this year (Delray Beach), which puts him one up on the likes of a number of more well-known players, including Grigor Dimitrov, Gael Monfils -- and the two other subjects of this column.

"It's a great feeling," Karlovic told the press after he set the new ace mark. "My serve is my biggest weapon and I always take pride in it. To be able to do this is a great feeling and a great accomplishment."

By the end of the year Karlovic had 10,442 aces and counting. Cha-ching!

Fabio Fognini

At the start of the year, Fognini was an interesting question mark. A stylish, mercurial Italian more given to clowning around than plowing opponents under, he was coming off a splendid 2014 during which he won the third singles title of his career and hit a career high of No. 13.

So what? In tennis, almost every decent pro goes on a run at least once in his career. The question lurking was, did Fognini, who would turn 28 in mid-2015, somehow turn a corner and become a mature competitor capable of harnessing all that flair and talent?

Rafael Nadal provided the answer -- much to his own detriment. The luck of the draw threw the men together five times in 2015 -- an astonishing frequency when you consider the odds -- with Fognini winning three of the encounters. The most significant of those was their third-round clash at the US Open.

Nadal lost that match in five sets, his first loss in 152 five-setters after being up two sets. It was an eye-opening, character-affirming performance that did wonders for Fognini's street cred. And the way he stood inside the court and hit a blazing stream of nearly flat, angled winners provided a template for anyone who would challenge a baseline muscleman. To many (including that struggle was the ATP match of the year.

Fognini is temperamental; he'll likely never travel on a smooth rankings or results trajectory. He's also 5-foot-10 and no powerhouse, so he's obliged to survive by his wits. But his matches against Nadal demonstrated that he's potentially much more than a quirky, entertaining journeyman. There's a seat waiting for him at the table where the elite pros play, if he's got the desire and determination to join their game.

Feliciano Lopez

Fognini, the man who knocked Nadal out of the US Open, was immediately beaten by Lopez in the next round. Like Karlovic, Lopez is defying the ravages of age.

It took Lopez, a lefty serve-and-volleyer, years to get where he is today, a good number of them more-or-less wasted. For long stretches he seemed content to live the comfortable, low-stress life of an in-demand, good-looking top 25 pro. Perhaps it's no coincidence that he's playing his most fearsome tennis now that he's settled down (Lopez married in July), although the quantum leap in his game traces to 2014. His results that year set the stage for Lopez to reach his career-high ranking of No. 12 early this year.

Lopez's success is largely due to his full embrace of the attacking style to which his game, with its lefty ju-ju and heavy underspin, is so well suited. Lopez also developed the mental and technical discipline required to play a game designed to get him to the net to end points with the volley. He's one of those players for whom it all came together late (in his case, very late), but he's certainly making the most of it.

Lopez had quality wins this year against Nadal (Cincinnati Masters), Milos Raonic (Cincinnati and US Open), Nick Kyrgios (twice), Kei Nishikori (Indian Wells) and Fernando Verdasco. Not bad for a guy playing an attacking style that some people say can't work anymore.