Story highlights Castro deadpanned he hadn't heard chatter about a 2016 bid with Clinton, before admitting he was kidding.

He also echoed Clinton's recently more contrite tone on her decision to use private email while in office.

Washington (CNN) Housing and Urban Development Secretary Julián Castro defended former Secretary of State Hillary Clinton on Friday morning on her use of private email -- as he also deflected chatter about him as a potential running mate to her presidential campaign.

When asked on CNN's "New Day" about being considered an appealing vice presidential candidate, Castro deadpanned: "I hadn't heard that before."

"I'm kidding," he added, cracking a smile.

But the former mayor of San Antonio and Democratic rising star said he was focused on his job in the administration right now -- though he did nothing to rule out the possibility of joining a Clinton 2016 ticket.

"That's very flattering, who wouldn't be flattered to hear that?" he said. "But I have learned in life that the best thing you can do to create a great future for yourself is don't forget what's in front of you. And so I'm trying to do a great job at HUD."

Read More