Rear grip is Honda's 2015 MotoGP weakness, says Marc Marquez

Yamaha has won three of the four grands prix held so far this season, with Marquez's Austin victory Honda's sole success so far.

Last year the team took 14 wins from 18 GPs - 13 of them, including the first 10 straight races, with Marquez.

The Spaniard said long-run pace was the key struggle, and admitted Honda's problems were compounded by the broken finger he suffered in a motocross accident before last week's Jerez race.

"At the moment our problem is the rear," he said.

"For some reason we are really strong on one lap but over the race distance, that is where we are struggling.

"But we are trying to work on it and we have some ideas. We didn't try them [at Jerez] because I was not sure with the finger and everything.

"We know where we need to improve and we will try to improve and avoid this problem and try to be stronger."

Marquez said he struggled with the greater physicality needed to ride the Honda with his injury.

"One thing is true - when we have problems, our problems are bigger because it's moving all the time," he said.

"When you are injured it's more difficult, like at the end of the [Jerez] race I was struggling on the straights, more than the corners, because I was struggling a lot with the wheelies."

Honda is currently 19 points behind Yamaha in the manufacturers' championship - a contest Honda has won every year since 2011.

Marquez reckons the Yamaha improvement was on the cards from late 2014.

"For me, already in the last part of last year Yamaha had a big improvement and looks like this year they are riding really good and really fast," he said.

The absence of Dani Pedrosa following his career-threatening arm pump problems has also hit Honda, with his stand-in Hiroshi Aoyama yet to finish in the top 10 in three outings.

RIDERS' STANDINGS SO FAR:

MANUFACTURERS' STANDINGS: