In the midst of celebrating the winning of this season's NBA championship, the Washington Bullets took time yesterday to try to head off potential weaknesses next season by picking Bradley guard Roger Phegley and DePaul center Dave Corzine on the first round of the league draft.

Phegley, a 6-foot-6, 205-pound sharpshooter who averaged 27.6 points his senior year, could be the other big guard the club needs, especially if Phil Chenier cannot come back from his back injury. Phegley was the 14th player chosen in the opening round.

Corzine, at 6-11, 250 pounds, is considered "out of the Wes Unseld mold" by General Manager Bob Ferry. He will be given a chance to back up Unseld while developing the potential he never seemed to reach in college. Corzine was the 18th pick the first round.

The Bullets chose another fine shooter, 6-7 Terry Sykes of Grambling, on the second round and 6-6 Rick Apke from Creighton on the third round. Later selections included Maryland's Lawrence Boston (fourth); Archie Aldridge of Miami, Ohio (sixth); Towson State's Roger Dickens and Georgetowns Ed Hopkins (seventh); Nestor Cora, St. Francis (eighth); Tim Claxton of Temple (ninth), and Steve Connor of Boise State (10th).

Ferry said he was reluctant to make any selection at first ("How do you improve a world title team?" he asked). When he finally decided to keep his top choices instead of trading them for picks next year, he went with Phegley, considered an outstanding prospect by experts, but relatively unknown nationally, and a reputed flakey character in Corzine.

"I was hoping Phegley would be available," said Ferry. "I've seen him play for three years and I like him. We've got a large guard (Chenier) who is hurt and who is working his way back. The only other big guard on the team is Kevin Grevey. We needed some insurance.

"I saw Roger score 50 points against Glen Gondrezick (now with the Knicks) in a college game. He's an excellent shooter, a good athlete, a solid, unspectacular player."

Phegley began his college career as a forward but said yesterday in telephone interview that he had played the last two years at guard. Although the Bullets feel he can swing between the two positions, Coach Dick Motta said Phegley would be tried first as a guard.

"I still have a lot to learn at guard but that's the position I like." said Phegley. "I've improved there and I know I can get better. I'll have to if I want to play in the NBA."

The Bullets had problems all season with their defense at guard, although it improved considerably during the playoff. After Chenier was hurt, Grevey was the only backcourt player left Motta could use against such opponents as 6-7 George Gervin, 6-6 Doug Collins and 6-4 Dennis Johnson.

Motta was forced to use forward Bobby Dandridge at guard during parts of the San Antonio and Seattle series, something he would like to avoid next year. Phegley acknowledged he isn't a great defensive player, but Ferry says he has "the desire and the ability to improve defensively.

The addition of Phegley, however, could make for a crowd at guard. If Chenier returns, the Bullets could have been guards on their training camp roster: Chenier, Grevey, Phegley, Larry Wright, Charles Johnson, Tom Henderson and Phil Walker. Motta carried five guards this season, so at least two probably will be cut or traded.

Phegley had a surprisingly successfuly college career. He originally went to Bradley, his hometown university in Peoria, Ill., on a baseball scholarship after being named most valuable player in the state tournament. But after playing with the school's varsity basketball players the summer before his freshman year, he wound up participating in both sports.

After averaging 8.1 points as a part-time player his freshman year, he improved to 17.3 his sophomore season, then 27.4 and 27.6 his last two campaigns. He was a 54 percent shooter in college and made 88 percent of his free-throws the last two seasons.

"I'm able to get open without the ball," he said in describing his style, which Motta likened to Jerry West's. "A lot of people can shoot when they have the ball but not that many work hard away from the ball to get open.

"At guard, I was able to use my size to take people down low. I have confidence I can bring the ball up. I don't have a favorite shot. I've had to shoot from everywhere on the court in college and that has helped."

Phlegley is a good outside shooter. Other then Grevey, the Bullets had to rely on small guards to supply their outside shooting in the playoffs.

Phlegley was drafted as a pitcher out of high school by the Cincinnati Reds. He said he didn't have many offers to play either baseball or basketball in college, "but the state high school baseball tournament was in Peoria and I guess Bradley had a scholarship left for me. Their basketball coach didn't think I was aggressive enough.

"I think I can help the Bullets. I have confidence in my ability and they must have confidence in me to pick me. Everyone is going to be shooting at them next year. Itwill be fun."

Corzine is the type of center who could fit perfectly into Motta's offense, which has the pivotman passing and setting picks more often than scoring.

Although Corzine has a fine shooting touch - he averaged 21 points and shot 55 percent last year - his best assets, according to Ferry, are his passing and intelligence.

"He is a great passer and he has a fine knowledge of the game," said Ferry. "He isn't a rebounder or outlet passer like Wes, but otherwise he is a lot like him. He has the ability to make others around him look good because he can pass and is smart. Wes has done that for us the last 10 years, so why not stay in that mold?

He (Corzine) isn't perfect. There are questions about his strength, agility and jumping ability. But it's worth a gamble for us to take a big man in this draft."

Ferry believes that Unseld, who has played out his option, will return next season. But Joe Pace, also a free agent, isn't expected back. Corzine would take Pace's spot and would allow Mitch Kupchak more time at forward.

Corzine had problems with motivation in his early at DePaul. But last year, when the club compiled the best record in the school's history, veteran Coach Ray Meyer said he was "the best player I've ever had here. He's a joy."

Motta said Corzine "can be a good player if he is surrounded by strength, like he will be here. By himself, he won't beat you. But he can fit in just as Wes fits in."

As always, Ferry used the later rounds of the draft to pick local players, including big men Boston and Hopkins. He also could have a couple of sleepers in Aldridge, a forward who was a top prospect last year but slumped this season, and Claxton, a good jumper and defensive player from Temple.