With everyone looking to challenge Mercedes this year in Formula One, former world champions Sebastian Vettel and Fernando Alonso will do so with new teams.
Here are some things to look out for in the upcoming season, which begins in Melbourne, Australia, on March 15:
BEST OF ENEMIES: Lewis Hamilton and Nico Rosberg went into last season on about as good a terms as any teammates can be at a top team, yet the inevitable pressures of fighting each other for the drivers' championship strained their relationship to near breaking point.
A collision between the pair at the Belgian Grand Prix forced Hamilton out of the race and left Rosberg 29 points clear at the top of the standings and seemingly headed for the championship. However, Hamilton responded by winning six of the seven remaining races to earn his second career title.
Preseason testing indicates Mercedes will continue to excel into the new season, at least in the early part, so another Hamilton vs. Rosberg title showdown looms.
Red Bull driver Daniel Ricciardo was the only man to take race wins off Mercedes last year, and the team is banking on an improved Renault engine to narrow the gap to Mercedes, but faces an uphill task to surpass the silver cars.
Ferrari, too, will be hoping for better things with the arrival of four-time world champion Sebastian Vettel, but it also has a lot of ground to make up in terms of engine development.
F1 fans would have been hoping for a broader mix of title contenders, but will likely have to settle on another intra-team battle. Rosberg will feel it is his turn this year, but can ill afford to give way to Hamilton, whose thrives on confidence.
PATIENT WAIT: On paper, the combination of McLaren, engine supplier Honda and two world champion drivers in Alonso and Jenson Button promises much.
McLaren won half of its eight constructors' titles with Honda, which is returning to the sport in 2015 after six years.
Alonso, having made way for Vettel's arrival at Ferrari, is also making a McLaren reunion, after one unhappy season with the team in 2007.
He and Button have competed in more than 500 F1 races between them, and are both drivers renowned for getting the most out of underperforming cars. That's a strength they may need to draw upon more than ever before as Honda plays catch-up on the design of the complex V6 hybrid-power engines.
Preseason testing exposed a slew of predictable teething problems, and things got even worse when Alonso suffered a concussion in a crash. The lingering effect of the concussion means he will sit out the season-opening race in Australia, to be replaced by Kevin Magnussen.
F1 HAS A NOSE JOB: After the major technical changes of 2014, when the sport ushered in its complex new engines, this season will have relatively minor alterations to the rules governing cars and racing.
The most apparent change is a return of noses tapering down to a low front wing, as the high fronts of recent years have been outlawed. It may have created a lot more work for aerodynamic designers, but is much more esthetically pleasing.
The restriction on pit-driver communication will be stepped up this year, with teams forbidden from sharing technical data like settings for fuel use. In a sport where exploitation of loopholes can often be the difference between success and failure, expect to see teams sailing close to the wind on that one.
The late afternoon start times for several races have been moved forward in response to the crash of Jules Bianchi last year in Japan. The French driver suffered severe head injuries when crashing into a trackside mobile crane in gloomy and wet conditions late in a race that finished near dusk.
Bianchi remains hospitalized in critical condition.
Colour CO-ORDINATION: A year after from introducing individualized driver numbers, Formula One now wants to force the sport's stars to stick with iconic helmet designs.
The proposed rule would severely restrict the number of design changes to helmets each season, to make drivers more identifiable both at the track and on television. The plan still has to be ratified by the World Motor Sports Council.
Sebastian Vettel regularly changed his helmet design when he was at Red Bull, with some innovative displays, and was not the only one to do so. Chopping and changing designs attracted interest, sparked discussion on social media and brought in some short-term sponsorship boosts, but for the watching public it also caused confusion as to which driver was which.
Some drivers have already grumbled about curbs on self-expression and restraint of trade, but the broader interest of fans and the sport seem likely to win out.
Bigger numbers on the cars could be the next step to helping fans.
MIND THE MANOR: Manor, the team that has raced under the names Virgin and Marussia in its five years in Formula One, is making a late bid to join the 2015 championship.
After sitting out the closing races last season with huge debts, the team looked to be following Caterham onto the long list of failed F1 ventures.
However, new ownership in the form of Stephen Fitzpatrick, head of the Ovo energy company, has arrived, chief creditor and engine supplier Ferrari has been appeased and the team is hastily preparing for the season ahead.
It has named Will Stevens -- who drove in the final race of 2014 for Caterham -- as one of its two drivers. No second driver has been named yet, and the late resolution of its 2015 entry and absence of preseason testing makes its claims of being ready to race in Melbourne seem very ambitious.
Teams can miss three races in a season without penalty, meaning Manor has until the Bahrain Grand Prix -- the fourth race of the season -- to be up and running.
