Walking on eggshells has become the way of life for the 2,800 staffers at the U.S. Postal Service here since Albert V. Casey -- who tells visitors that friends describe him as "lovable" -- took over as postmaster general.

In November workers were jolted by the announcement of a reorganization that could send as many as 200 Washington- based aides to the field.

Since then, Postmaster General Paul N. Carlin, who announced the mini-shakeup, has been replaced, partly because the board of governors felt he wasn't moving fast enough to cuts costs and trim management fat from the government-owned corporation, which has more than 700,000 employes. Many workers who were nervous and angry in November now remember that time fondly as the good old days.

Now with Casey, a veteran executive with American Airlines, the Southern Railway and the Times Mirror Co., at the bat, the Postal Service may face even bigger job cuts. Carlin was a career employe who planned to stay a long time. Casey already has a top university job waiting for him, and has fewer ties to the service's career management staff or rank and file.

Some members of the board of governors are pushing to have nearly one of every three headquarters positions abolished along with the district office command structure.

The Postal Service chain of command goes from headquarters to its five regional offices, to 42 district offices to 225 sections centers, including places such as the Northern Virginia area of Merrifield and the sectional center in Riverdale.

When it announced the headquarters reorganization last fall, the Postal Service asked for permission to offer early retirement to employes at least 50 years old with 20 years' service, but was turned down by the Office of Personnel Management. OPM said the reorganization wasn't significant enough to warrant the early retirements.

That, plus Carlin's replacement by a hard-driving short-timer, has prompted many postal veterans to speculate that the next step could be a major reduction in force at headquarters, which would qualify it for early retirement authority.

"The people downtown in other federal agencies are worried about taking a 3 or 4 percent hit because of the Gramm-Rudman-Hollings Act," a career postal official said yesterday. "We think they have it made. We would be delighted if that was the only sword hanging over us."