"It's pretty obvious that the political knives were out for Chuck Hagel," Panetta said on NBC's "Meet the Press," after being asked about the negative comments by GOP Sens. John McCain of Arizona and Marco Rubio of Florida following Hagel's confirmation hearing before the Senate Armed Services Committee last week.
Panetta, who said he believes Hagel, a former Republican senator from Nebraska, is fully prepared to take his place, was disappointed that the hearing concentrated on past issues.
"But what about what a secretary of defense is confronting today," he said. "What about the war in Afghanistan? What about the war on terrorism?"
Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said he was surprised some issues, including Afghanistan, were not discussed in depth.
Dempsey also said Hagel has been very well-prepared and thoughtful in his dealings with him.
"I'm not going to speak about confidence. He could be my boss. And when is the last time you saw a subordinate discuss their confidence in their potential boss?" Dempsey said. "But I think he's got great credentials, my personal contacts with him have been very positive. And if he's confirmed, I look forward to working with him."