Reliability issues for Ferrari have effectively handed the title to Mercedes driver Lewis Hamilton, says Jenson Button.
Hamilton has opened up a 59-point advantage at the top of the standings having won four of the five grands prix since the mid-season break, while Vettel's challenge has slipped as a result of engine problems.
After crashing out in Singapore, the German had to fight from the back of the grid for fourth in Malaysia and was unable to finish in Japan.
Hamilton can consequently clinch a fourth world championship if he wins this weekend's United States Grand Prix and Vettel finishes sixth or lower.
Button believes his former McLaren team-mate would be a worthy victor but laments the impact Ferrari's troubles have had on an enthralling title race.
"In terms of the fight this year, it's good that we have another team that's challenging Mercedes and Lewis. I think that keeps people interested," Button told Omnisport at an event to promote his new book.
"I've watched every race. I didn't think I would, but I have, because I love that fight between two manufacturers, two great drivers, but I think that's what people will turn on to see.
"It's a shame that Ferrari have had the issues they've had the last couple of races and Sebastian obviously with the incident in Singapore because they've been quick, they've just made mistakes and sort of handed it more to Mercedes and Lewis.
"But if Lewis does win the championship, which I think he will, it's very well deserved. I think the last two years he's been driving very well, very confident it seems in his ability.
"Last year he was just really unlucky with reliability issues but this year it's just run smoothly and perfectly for him. I hope he clinches it."
Button has admitted to concerns the title was going to get away with him in 2009, when he failed to guide his Brawn GP to the top step of the podium after triumphing in six of the season's opening seven grands prix.
Asked if Hamilton could have similar worries as the season enters its closing stretch, he said: "No, because his car is still the quickest.
"We were so far off the pace by the end of the season. We didn't have the funding that Mercedes has. We spent very little during the year so we didn't develop the car.
"It's dangerous to stand still in Formula One because everyone's improving the whole time. For us it was very difficult at the end of the year.
"For him they have the best car, or maybe second-best car, so he's just got to be consistent and finish."
Jenson Button's new book 'Life to the Limit: My Autobiography' from Blink Publishing is available now.
|World Cup exit not a negative, insists Kiwis skipper Blair|
|Kane & Alli fit for Spurs at Arsenal, Lacazette starts|
|Sri Lanka close in on first-innings lead in Kolkata|
|Sydney leapfrog slapstick Jets at A-League summit|
|Hamilton: I learned nothing from Rosberg|
|Christensen guides the way for Loftus-Cheek & Abraham at Chelsea|
|Mertens: Sarri´s tactics give Napoli 12 men|
|Bayliss finds positives despite England´s toil|
|Aubameyang back in Dortmund fold pre-Spurs|
|Hafeez should give up bowling after third suspension – Akram|
|Moses heartbroken as Lebanon come up short|
|Fiji upset New Zealand in World Cup quarter-final|
|Marsh desperate to take Ashes chance|
|England struggle in draw against CA XI|
|Spurs erase 23-point deficit to beat Thunder|
|Tonga edge Lebanon to reach World Cup semis|
|Davis suffers concussion against Nuggets|
|Bosz laments ´ridiculous´ goals|
|Broncos GM Elway calls team ´soft´|
|Madrid have best kids stockpiled – Simeone|
|Guardiola backs Stones to get even better|
|Ibrahimovic will start with bench role, says Mourinho|
|Injections to play a friendly – Mourinho slams England over Jones handling|
|Chargers´ Rivers cleared to face Bills|
|Cook grabs RSM Classic lead|
|Nets PG Russell undergoes successful surgery|
|Championship Review: Sheffield United go top|
|Gloucester´s second-half surge stuns leaders Saracens|
|Schurrle: Dortmund couldn´t deal with Stuttgart counter-attacks|
|Conte laments Italy World Cup failure|
|Murray splits with coach Lendl|
|Hartley´s Toro Rosso deal will not affect Porsche status|
|Amiens 1 Monaco 1: Jovetic rescues point but champions give PSG boost|
|Dimitrov eager to keep momentum going after easy Carreno Busta win|
|Stuttgart 2 Borussia Dortmund 1: Bosz pressure builds after more Burki mishaps|
|Sunderland target Coleman steps down as Wales manager|
|Memorable Ashes Moments: Harmison sends down woeful opening wide as England´s defence wilts|
|Conte´s wife tells him to grow a beard – Conte grows a beard|
|Simeone rules out Everton job, promising ´a couple of years at least´ at Atletico|
|Pique to miss Barcelona´s Leganes trip over personal matter|
|Serena Williams reportedly marries Alexis Ohanian in New Orleans|
|UEFA closes Roma ´monkey chanting´ case|
|Swinson set to miss Six Nations after finger surgery|
|Don´t worry about Messi renewal, Valverde tells Barcelona fans|
|Cheika disrespected referee - Jones|
|´Griezmann? We´ll see´ – Valverde won´t rule out Barcelona pursuit of Atletico star|
|Cardinals & Larry Fitzgerald agree to 2018 contract extension|
|Uncapped Enever replaces injured Coleman for Twickenham clash|
|Goffin overcomes slow start & Thiem to set up Federer semi|
|Unsworth surprised to see Allardyce snub Everton|
|Six-week stadium ban for Sale boss Diamond|
|Mourinho has ´immense respect´ for Benitez|
|Howe backs Defoe to make World Cup squad|
|Everton speculation out of my control - Silva focusing on Hornets|
|Conte concerned by Manchester City´s breakaway lead|
|Man City results ´perfect´, but Guardiola demands improvement|
|David Luiz back in Chelsea squad, Conte confirms|
|Recovered Klopp offers Liverpool fitness update|
|Guardiola confident Aguero in ´perfect´ condition despite hospital trip|
|Ibrahimovic, Pogba and Rojo back for Manchester United|
|Fleetwood and Rose look set for desert duel, Fitzpatrick leads in Dubai|
|Heynckes compiling list of potential successors|
|Modric & Carvajal fit for Madrid derby|
|Bayern begin talks over Wagner deal|
|Pulis angered as Chadli sidelined for ´foreseeable future´|
|Neymar to join Ronaldo at Real Madrid? Zidane speaks out on PSG star|
|Edinburgh banking on Barclay after signing Scotland captain|
|Guardiola & Sane complete Man City award double|
|Five-try Holmes makes history as Kangaroos batter Samoa|
|Brave Chapecoense secure top-flight status|