Who knows whether the gods will add tomorrow to the present hour? -- Horace

In the annals of sport, no job, perhaps, is as tenuous as that of the 10-day man in the National Basketball Association. He gets a cup of coffee in the big league, but hardly time to stir.

When Claude Gregory signed a 10-day contract with the Bullets recently, he kept his apartment in Evansville, Ind., where he had been playing for the Evansville Thunder of the Continental Basketball Association. Sure enough, he needed it.

"You don't promise yourself anything, especially if you don't have anything that says 'guarantee' on it," said Gregory, who returned a call as soon as he had rolled back into Evansville after an all-night bus ride from La Crosse, Wis., and a game with the La Crosse Catbirds. "It's not like the NBA."

In contrast, Kevin McKenna, a 10-day man fresh from the CBA's Kansas City Sizzlers, had the better fortune of gaining a contract with the Bullets for the rest of the season -- a decision the team made even before McKenna scored 25 points Feb. 17 to make the difference in the Bullets' 96-94 victory over the Los Angeles Clippers. As good a shooter as he may be, McKenna got his rest-of-the-season opportunity mainly because there was an opening on the roster created by an injury to Frank Johnson.

"It's almost like when you go fishing," said Bullets General Manager Bob Ferry, who has signed four players to 10-day contracts this season. "They're not all 'keepers.' You throw some back."

Starting in December, an NBA team can offer a player a 10-day contract, and can keep him on a second 10-day contract. The player makes about $4,000 per 10 days, a salary prorated on the NBA's minimum annual player's salary of $70,000. If the short-term player is still around after 20 days, the team must drop him or sign him to a contract for the rest of the season.

An NBA team can sign as many 10-day players as it wants, or as Ferry says, "As many as I don't want." To him, signing a 10-day man usually means the team has been hit with an injury.

"I would say more than 50 percent of the time it's a question of a player being used just for practice," said Ferry. "You have a 12-man roster, and if you have one or two players with minor injuries who can't practice, you need to have a workable number for practice.

"They come in with a lot of hope," added Ferry. "But you don't really want to tell them what their chances are of sticking."

No 10-day player has achieved stardom, but several are carving out fairly solid careers. Ferry points to Charles Jones, a Bullet ever since he joined the team last season as a 10-day player.

The practice of signing players for 10 days is "good and bad" in the opinion of Larry Fleisher, the NBA Players Association general counsel. "There are some players who have gotten full-season contracts," he said, "but many of them are used as cannon fodder."

As the lives of 10-day men go, it has been about as good as it gets recently. Following McKenna's heroics on a Monday night, 10-day man Michael Holton won a game for the Chicago Bulls two nights later with 18 points, including a last-minute, game-deciding basket. More often, it goes as it did for the Bullets' first three 10-day men this season: Freeman Williams, Ennis Whatley and Gregory. "Last man hired is the first man fired," said Gregory, with a laugh.

Gregory, who played at Coolidge High here and later at Wisconsin, stayed with the Bullets for a second 10-day contract, but then it appeared the injured Jeff Ruland was ready again. It was back to the CBA for Gregory.

He left with the small solace that he had been voted to the CBA all-star team and would report directly to Tampa, site of the all-stars' game against the first-place Tampa Bay Thrillers. "I didn't want to go . . . But instead of sitting around moping and groping, I said, 'We'll go to Florida.' " From 1981 to 1984, the 6-foot-9 forward played in Italy and Spain -- but that was enough. "I guess I wanted to get back to the United States. The ultimate in basketball is the NBA."

So, Gregory plays on with the Thunder in the hope of winning one more chance. "I always keep positive vibes," he said.

Gregory had come to the Bullets after Williams and Whatley had gone out the revolving door of 10-day players. Williams answered the Bullets' call for a back-court man, got 17 points off the bench against New Jersey in his first appearance to lift the Bullets to victory and received a second 10-day contract. But in a matter of days, Williams surveyed his situation. "They had five guards," he said. "I figured that I would be the one who left." So he went, back to Tampa's Thrillers.

Sometimes, however, the nomadic existence pays off, at least to some extent. Jeff Lamp, former University of Virginia star, recently caught on for 10 days with San Antonio after being cut by Milwaukee -- and the Spurs now have contracted him for the rest of the year. "It's another opportunity to get back in the NBA," said Lamp.

After three seasons, Lamp was dropped by Portland, and last year he was out of basketball entirely, finishing up his credits for his degree at Virginia and working in commercial real estate in Portland. He thought maybe he was through with professional basketball. But he got the urge.

"I played in the Los Angeles summer league last summer. Milwaukee gave me a tryout. I stuck with them until just before the all-star break." Then San Antonio called, he reported, got "some good minutes" -- and now he has the rest of the season to prove himself. "There's a little bit of pressure to produce in a 10-day situation," Lamp said. " . . . You come in in the middle of the season and there's no luxury of learning the plays over an extended period of time."

That's the hard part, according to the newest Bullet, McKenna. With little time for preparation, the problem is "knowing the exact place you're supposed to be on each play."

McKenna, who has played also for the Los Angeles Lakers and Indiana Pacers, went through the 10-day experience last year with the New Jersey Nets. The Nets kept him for two 10-day periods, then dropped him, then brought him back to finish the season. "Coming in with the Bullets, I just thought if I played well, who knows what might happen? Some team might see something, the Bullets might see something."

Because he wasn't ready to give up on his NBA dream, McKenna had gone to the Kansas City Sizzlers and was averaging about 25 points his last six games there. "There's a lot of good players in the CBA," he said. "But the travel -- it's tough. Mentally, it's more demanding than anything. When you're used to the NBA, you're kind of spoiled a little and you want it that much more. The food money's about half. The pay is one-millionth, it seems. Every day is another drudgery."

The Bullets are the first team to try the 6-7 McKenna as a guard. He likes the idea. And Ferry declared McKenna's performance against the Clippers, which included five three-point field goals, nothing short of "great."

"The Bullets have given me a contract for next year," McKenna said. "It's not guaranteed, I have to make the team. But this is the first time a team has shown an interest beyond the season.

"They seem genuinely interested. I'll be happy to come to Washington next July for training, weights. That will keep me going through the summer. Before it was always, 'I'm working out, but will I get a chance?' "

At least he's got more than 10 days.