Ridge said he had known Hagel, a former Republican senator from North Platte, Neb., since the 1980s. Ridge was then a congressman from Erie and Hagel was in charge at the USO.
He said Hagel would not hesitate to speak his mind to President Obama.
"You've got to speak the truth, and you've got to speak it candidly," he said. "I don't think the president will walk away from any conversation with Chuck Hagel not knowing what he meant."
Ridge said he agreed with many Washington Republicans in working to block Obama from appointing Susan Rice, the U.S. ambassador to the United Nations, as secretary of state.
While noting that some Democrats had also come out against Hagel's appointment, Ridge was critical of what he saw as overwrought GOP opposition to Hagel.
"I, for one, thought it was very appropriate for many reasons to block Susan Rice," he said.
"But I think in this instance the president has made the decision, and, absent something out there of which I am totally unaware, I think he is entitled to his choice.
"I wish my Republican colleagues would have spent this kind of enthusiasm and energy dealing with the fiscal crisis, but that's another story. I think the man deserves to be approved by the Senate."
Hagel, who served in an infantry unit and was wounded in action, will bring a sergeant's perspective to the Pentagon in addition to his Senate experience, Ridge said.
"Does it have a bearing? I think it does," Ridge said. "Three hundred million citizens in America - how many have faced combat? . . . You don't necessarily dwell on the experience, but you can draw from it."
"You can have all the Air Force generals thinking how nice it is lobbing in missiles from 20,000 feet. I think having had boots-on-the-ground experience is valuable."
Ordinary soldiers would approve, he said: "You've got to believe the NCOs and the enlisted men of the military will be thrilled to have a former NCO and enlisted man as 'sec def.' "
Contact Tom Infield at 610-313-8205 or firstname.lastname@example.org, or follow on Twitter @tinfield.