Martin Truex Jr unsure why NASCAR title defence has been tough so far

Truex's best result of the year so far came at Las Vegas with fourth after finishing fifth at Atlanta and a lowly 18th in the season-opening Daytona 500.

The Furniture Row Racing driver has also endured problems on pitroad in the last two races as well as handling concerns, and failed pre-race inspection at Atlanta.

Ford and Chevrolet have both won races this year, with Toyota yet to do so after it and Truex dominated the 2017 season.

When asked if he thought other teams were now ahead of his Furniture Row outfit, Truex said: "I don't know if they've picked it up quicker than we have or the rules have benefited their body style more than it did ours.

"We had to change some things from how we did them last year and it appears those guys are really quick right now.

"We have to hand it to them, they did their homework and they're really fast and they're doing a good job.

"I'm not going to be the one that sits here and says there's an unfair advantage because I haven't figured that out yet."

Truex has pinpointed handling problems as the reason why he has only led 11 laps in 2018.

"We're going to go back to work and we've got some things coming that we've been working on," he said.

"We're right there, we just can't get the balance of our car where we need it.

"[I've] just been struggling with getting it to turn good enough these last two weeks and when we get that figured out we'll be right there with them."

He added that his downturn in form will not matter until the final 10 races of the season when NASCAR enters its playoffs phase.

"It's a marathon and it's a grind, honestly it really matters where you're at when those last 10 races start and I've learned that over the past few years," he said.

"Obviously you want to run good, be consistent and get stage points and all those things, but we'll get there.

"Hopefully we'll get a few wins along the way, but we know when it really matters is later in the season."