Jenson Button can win races again with McLaren-Honda, says Nigel Mansell.
The team announced on Thursday that Button will be staying with them for 2016 and Mansell said the news was "brilliant for Honda, brilliant for McLaren and brilliant for Jenson".
McLaren have struggled badly in 2015 and are ninth out of 10 teams in the constructors' championship.
"Jenson deserves an opportunity to see if they can compete and win next year," the 1992 world champion told BBC Sport.
"I think this winter Honda can make a breakthrough and McLaren will be working so, so hard. They are a fantastic team.
"They've won so much in the past and, to use [McLaren chairman] Ron Dennis's words, they will win again in the future. I have no doubt about that."
'Frustrated' Button and Alonso 'need patience'
Button, the 2009 world champion, and team-mate Fernando Alonso, who took the title in 2005 and 2006, have both expressed their frustration in recent races at the lack of performance from the McLaren and, particularly, the down-on-power Honda engine.
The 35-year-old Briton's future had been in doubt while Spaniard Alonso, who described his car as "embarrassing" during Sunday's Japanese Grand Prix, said afterwards he "didn't know" whether he would be racing in F1 next year.
Mansell said "they are quite right to express their frustration" but urged McLaren's drivers to "stay the course" as "both have enormous ability to win further World Championships".
He added: "Between Alonso and Jenson they will be a formidable team, given the car and the engine to do the job.
"When you go through the growing pains, and I've been there a few times myself, stay the course because they could have the best team and best engine and they'll have some really serious regrets if Honda get it right after they've gone somewhere else.
"Hopefully within 12 months they'll be singing the praises of the team and Honda. I sincerely hope they'll be winning races in a year's time."
'I was wrong to quit McLaren in similar situation'
Mansell joined McLaren in 1995, aged 41, as they were starting a new engine partnership with Mercedes, which lasted until 2014 and brought the team three drivers' titles and one constructors' championship.
The Briton was forced to miss the first two grands prix of the season as the car did not fit him and after returning for two uncompetitive races, Mansell decided to quit McLaren and retire from F1.
He says now he was wrong to do so and should have stayed at McLaren to help improve the car.
"I have to say, unequivocally, that given the same set of circumstances what I should have done, and didn't do, is sit in the office for a day or so to have a good chat with Ron Dennis. He would have helped me enormously and the chances are I wouldn't have stood down at that time," he said.
"That's why I give this advice to everybody now to think very carefully."
|279 Formula 1 starts||1 world championship (2009)|
|15 grand prix wins||50 podium finishes|
|8 pole positions||8 fastest laps|
Mansell used Honda engines from 1985-87 when he drove for Williams and says the Japanese manufacturer is "going through the same challenges" they experienced when joining Formula 1 in that decade.
He added: "I believe that if the iron will is there, which I've witnessed before from McLaren and Honda, they will get it right."
Mansell said Honda would find it easier to improve their power unit if restrictions were eased to allow more in-season development and he urged governing body the FIA to encourage new entrants.
"There should be a better mechanism for new manufacturers to come into F1 and not be given a hard time like Honda when they are trying to get up to speed," he said.
"We should be embracing them and cutting them and McLaren some slack to be able to develop the engine so they can start to compete. We need them."
Red Bull-Toro Rosso quit threat 'very worrying'
Red Bull and sister team Toro Rosso have threatened to quit the sport at the end of the season unless they can secure a competitive engine partner and Mansell said he was worried that F1 could be left with a sparse grid.
"We have only got 20 cars on the grid. I am concerned because we want to attract more teams and more manufacturers to F1. Until there are at least 26 cars on the grid everyone should pay attention. It is a must that the teams and manufacturers are there year after year," he said.
Red Bull are on the verge of splitting with current engine partner Renault, despite winning four consecutive world championships from 2010-2013. Ferrari have offered to supply them with year-old engines in 2016, but the Milton Keynes-based outfit want the latest specification.
Mansell said: "Red Bull are a winning team, they want to win and have the power of everybody else. Hopefully it will all be sorted out behind closed doors.
"It's an unfortunate set of circumstances where all the engine rules changed in the last couple of years and one or two manufacturers are head and shoulders above everybody else."
'Take away the driver aids'
Mansell, who won 31 grands prix in an F1 career that lasted from 1980 to 1995, is not happy that current drivers have to race cautiously to preserve fuel and tyres, while receiving regular instructions from their team over radio.
He said: "The polite word is awful. I like the drivers to race and drive the cars themselves and not be told how to drive it. There are something like 350 settings on the steering wheel now backed up by 30 to 50 engineers telling the driver 'change this, do that, do the other'.
"I'd like the driving to be more in the hands of the driver and less in the hands of the engineers. Sometimes I'm disillusioned that the driver doesn't have the ability to show how great he is. We used to drive around problems - we couldn't alter the car as such when we were driving.
"Sometimes I want to see how great and courageous they are. Most of them are great, courageous drivers but we never get to see that. Take a lot of the aids away. Let the driver manage the car himself."
Mansell said current supplier Pirelli had done a "sterling job" making tyres that deliberately degrade during races, but would be happy if F1 switched to Michelin from 2017, as several leading teams wish.
"To go back to a tyre manufacturer that, historically, has a better, consistent tyre that can possibly last longer will be good for racing," he added.
'Lewis Hamilton in a league of his own'
With reigning champion Lewis Hamilton holding a 48-point lead over Mercedes team-mate Nico Rosberg in this year's standings with five races remaining, Mansell says it is a "done deal" that the Briton will retain his title.
He makes Hamilton a "hot favourite" in 2016 as well but is encouraged by the progress of Ferrari and Sebastian Vettel and is hopeful that Mercedes will face tougher competition next year.
"Lewis is in a league of his own but that's because he's able to refine his talent incredibly with the support of Mercedes and knowing he has got the quickest car," said Mansell, who has just released his autobiography Staying on Track.
"Sebastian Vettel is doing an absolutely wonderful job with Ferrari. They are pushing hard but are not quite on the same level as Mercedes. In isolation in 2015, Lewis is out there on his own. At times Seb is right there with him.
"Lewis is having a wonderful time, exploring life and having fun. For me, having fun makes you a better person. It makes you want to go to work and put it out there even more. When Lewis is on it, he is on it."
Mansell said that Rosberg, who has been out-paced and out-raced by Hamilton in 2016, "needs to pay attention to what he's doing more than what Lewis is doing".
He added: "He's won some great races and he can give Lewis a much bigger challenge if he just focuses himself."