CONCORD, N.C. – Car owner Rick Hendrick isn’t throwing a tantrum but he’s not pleased with his team’s performance this summer and vows to “step it up’’ as a leader.

Hendrick Motorsports has won once in the last 12 NASCAR Sprint Cup races and his four drivers – Jimmie Johnson, Jeff Gordon, Dale Earnhardt Jr. and Kasey Kahne – have combined to lead seven laps in the last two months.

“We’ve just fumbled the ball more than normal,’’ Hendrick said Tuesday after a groundbreaking ceremony for an Axalta Customer Experience Center on the Hendrick Motorsports campus. “The true character of an organization and a team is how you fight back.’’

Hendrick blames himself for his team’s struggles.

“I take more of the blame than anybody else because I am the leader,’’ said the 11-time Cup champion car owner. “That’s my responsibility, and I aim to step it up.’’

Hendrick Motorsports’ performance has not been encouraging this summer. Earnhardt’s average finish since winning the July Daytona race is 11.3 – best on the team. Johnson is next at 15.5, followed by Gordon (19.4 average finish) and Kahne (24.8) during that same time.

“People catch up, people work hard, rule packages, rule changes, usually we’re on top of it, usually we come out on front,’’ Hendrick said. “To think that you can be in this sport every single year and be the dominant guy that wins them all, it ain’t going to happen. NASCAR isn’t going to let that happen.’’

Darlington continued Hendrick’s struggles. Earnhardt was the only Hendrick driver to finish in the top 10, placing eighth.

“We get in position like in Darlington when we have three in the top six or seven and we run out of tires,’’ Hendrick said. “That’s our fault. Jimmie spun and we used a set there. Maybe we didn’t use the right strategy. Who knows? There’s been a lot of that this year.’’

While Hendrick has struggled, Joe Gibbs Racing has excelled, winning seven of the last 10 races, including Carl Edwards’ victory in last weekend’s Southern 500.

Gibbs has all four of its cars qualified for the Chase, while Hendrick has only two – Johnson and Earnhardt. Gordon clinches a Chase spot by finishing 17th or better Saturday night at Richmond International Raceway (which can be seen on NBCSN). Kahne must win to make the Chase.

A victory by any of them would still leave the organization short of where it was last year. Hendrick mentioned how his teams had 10 wins at this point last year. They have six this season – four by Johnson and two by Earnhardt.

“I don’t like to lose, I’m very competitive,’’ Hendrick said. “We’ve got to go to work. We’re looking at everything. I’m spending more time with them to make sure they know that I have their back

“It’s not broke. We’re off a little bit. I don’t know if we’re off. Maybe we’re the same and everybody else is better. We’ve had a lot of success and these people want it and they want it bad. They have a lot of pride and they don’t like to be beat.’’

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