The top 10 drivers of IndyCar 2015

The 2015 IndyCar season will forever be overshadowed by the loss of Justin Wilson, in a tragic accident that rocked the series and re-opened a long-running debate on driver safety.

After Pocono, though, came Sonoma - a championship finale that yielded an unlikely champion - and, as AUTOSPORT's IndyCar correspondent Mark Glendenning explains, a surprise number one in his yearly driver ratings.

1 GRAHAM RAHAL
Team Rahal Letterman Lanigan Racing
Starts 16
Wins 2
Position 4th

Rahal might seem a strange choice for number one, considering he only finished fourth in the points. Then you dig out the microscope.

He visited the podium more times than anyone else, matched Montoya's tally of two wins, and did it all despite driving for a one-car team using the inferior Honda engine and aero package.

There were lucky breaks, like the non-penalty at Fontana, but they were balanced by weekends like Pocono, where he was taken out by Tristan Vautier.

And most crucially of all, he stepped up as a driver. A lot of questions have been asked about Rahal in recent years, with good reason. In 2015, he finally started to answer them.

2 SCOTT DIXON
Team Chip Ganassi Racing
Starts 16
Wins 3
Position 1st

The Kiwi is so laid-back he can do remarkable things, like win a fourth drivers' title, and yet you barely notice him until he's celebrating on the podium.

He notched an early win at Long Beach, later added another at Texas, and finished with a victory at Sonoma: a street course, an oval and a road course. The dips in between were mostly due to bad luck, like getting wiped out by team-mate Charlie Kimball in Detroit.

When it came down to it, there were many who suspected Dixon was the only person who could beat Montoya to the title in Sonoma. And they were right.

3 JUAN PABLO MONTOYA
Team Team Penske
Starts 16
Wins 2
Position 2nd

The Colombian led the championship from the first race right through to the halfway mark of the finale in Sonoma, where he was derailed by a friendly-fire incident with Will Power. And he won the Indianapolis 500.

Those two facts alone make for a pretty spectacular comeback season by a driver on the verge of turning 40. That he was in control of the points for so long and then failed to close the deal will stand as one of the great stumbles in modern motorsport.

If the clash at Sonoma was the tipping point, it was the string of indifferent results after Indy that left him exposed in the first place.

4 JOSEF NEWGARDEN
Team CFH Racing
Starts 16
Wins 2
Position 7th

This was a breakout season for Newgarden: he earned his first two career wins, and did it with one of the less-resourced teams on the Chevrolet side of the divide.

Indeed, had CFH Racing been a little sharper in the pits he might have scored a lot more points, but the mere fact that he went into the finale as a mathematical contender was a huge testament to his performance.

He's already known to be on the radar of the bigger teams: the big question going into the winter is, can any of them find space for him in 2016?

5 WILL POWER
Team Team Penske
Starts 16
Wins 1
Position 4th

Power came into the year as defending champion, and finished it with a self-assessed rating of six out of 10. And that seems fair.

He held off Rahal for what would prove to be his only win of the year on the Indianapolis road course, but it's amazing to think that he only found the podium on two other occasions (and none at all after the Indy 500, where he narrowly lost to Montoya).

Elsewhere, there was a lot of misfortune: the pitlane spin at Long Beach, or getting crashed into in Detroit, Fontana and Milwaukee. The curse of No.1 lives on.

6 RYAN HUNTER-REAY
Team Andretti Autosport
Starts 16
Wins 2
Position 6th

If you want to get a sense for how long it took Andretti Autosport to wrap its head around the Honda aero kit, consider this: rounded up, Hunter-Reay's average finishing position over the last four races was third. During the 12 races prior, his average finishing position was 13th.

True, it's an imperfect measure, but it's accurate enough to illustrate the general point that Hunter-Reay and Andretti ended the year in much better shape than they started.

Hunter-Reay can't shoulder all of the blame, but with RLL making so much of the same technical package, the 2012 champ has to view this year as an opportunity wasted.

7 HELIO CASTRONEVES
Team Team Penske
Starts 16
Wins 0
Position 5th

The Brazilian's recent campaigns have been built on a foundation of consistency rather than speed, and that relentlessness was still evident in 2015: he was on the podium five times, including three second-places.

But for the first time since the arrival of the DW12 in 2012, he never reached Victory Lane.

His tally of four poles would suggest that there was nothing wrong with the car's pace on new tyres, so the question he and Penske will be working over the winter to answer is why they had such a hard time translating those into wins.

The occasional slip-up, like torpedoing Scott Dixon on the Indy road course, didn't help.

8 MARCO ANDRETTI
Team Andretti Autosport
Starts 16
Wins 0
Position 9th

When everything was working properly, Andretti was more competitive this year than his final finishing position of ninth in the championship would suggest.

He was one of the earliest - and most vocal - critics of the Honda technical package, and there were certainly a few weekends when his performance would have been rewarded with a better result had he been driving a car carrying the other badge.

He also seemed prone to catching the wrong end of the yellows, and while a strategy gamble helped him onto the podium in Detroit, it was his fighting third at Fontana that offered the best glimpse of what might have been.

9 TONY KANAAN
Team Chip Ganassi Racing
Starts 16
Wins 0
Position 8th

Aside from a horrible couple of weekends at Indy and Detroit, the Brazilian veteran was a rock most the way through the season: a guy who you could always rely on to be somewhere in the middle of the top 10, and capable of snatching a podium when the opportunity presented itself.

Whether that's good or bad rests largely on your expectations, and whether you're judging Kanaan by his own recent history, or by the history of the No.10 Ganassi car that carries him.

There should still be a few wins to come from the 40-year-old yet, but if 2015 is any guide then it's an open bet as to whether the future holds another full-tilt championship challenge.

10 SEBASTIEN BOURDAIS
Team KVSH Racing
Starts 16
Wins 2
Position 10th

An erratic season from one of IndyCar 's most enigmatic drivers.

KV is a team with some obvious limitations, and Stefano Coletti's value to Bourdais as a team-mate was difficult to discern.

And yet the Frenchman was able to win a crazy race in Detroit, and then dominate at Milwaukee, of all places.

It's telling that those two wins also represented Bourdais' only visits to the podium this year: the rest of the time he was usually scrapping around in the lower edges of the top 10.

Punting Graham Rahal at Sonoma wasn't the greatest way to end the season. Get all the ducks lined up though, and he's a match for anybody.

SPECIAL MENTIONS

Gabby Chaves had little to show for the season in terms of outright results, but his quietly assured performances with the relatively small, single-car, Honda-aligned Bryan Herta Autosport team won him a few admirers in the paddock.

He only cracked the top 10 twice, but the fact that they were at venues as vastly different as Detroit and Texas points to encouraging things for the future, and the team is already close to having everything in place to retain him for next year.

Sage Karam was a little harder to miss, for both good reasons and bad. At his best, his raw speed and absolute refusal to be intimidated by his more experienced peers made him thrilling to watch, and while the highlight of his year was the third place at Iowa, he often ran high up the order elsewhere before being derailed by some disaster or another.

There were times when his aggression got the better of him: he later admitted that he "drove like an idiot" in Detroit, and he had his share of critics at a couple of the ovals. Karam is very much the rough talent in need of some polish, but with Ganassi yet to firm up the funding for a fourth car next year, it's an open question as to how and when he's going to get it.