The 18-year-old cocaptain of Alexandria's nationally ranked T.C. Williams High School football team was arrested in a police drug sweep yesterday and charged with possessing cocaine with intent to sell.

Tracy Fells, an All-Met and All-State defensive tackle who led his team to an undefeated season and the state championship last fall, was arrested by Alexandria police in the city's Lynhaven section, in the northern part of the city that has several well-known drug markets. Police spokeswoman Lucy Crockett said that officers confiscated about $4,000 worth of crack, a cocaine derivative, when Fells was taken into custody.

Fells, who was being held in Alexandria Jail last night under $5,000 bond, was one of 21 arrested yesterday in several known drugs markets in the city, police said.

In a busy day for area drug enforcement officials, 20 people in the Mount Vernon neighborhood of Fairfax County were arrested on more than 40 drug-related charges, most of them for distribution of cocaine and crack. Also yesterday, five Washington men were convicted in D.C. Superior Court of conspiracy to distribute cocaine and other charges. {Stories on Page G5}

Fells' arrest follows by less than two weeks the drug-related death of Rico Leroy Marshall, an honorable mention All-Met player and a standout running back at Forestville High School in Prince George's County. Marshall, 18, died Feb. 13 after telling a friend he had swallowed several chunks of crack after police spotted him in an area known for drug sales. In December, Marshall, at that time a juvenile, was charged with possessing 29 grams of crack.

Marshall's coach, Eric Knight, was suspended this week from Forestville High for omitting from his 1975 school job application a 1974 conviction for conspiracy to possess drugs.

Friends and coaches of Fells, a T.C. Williams senior, described him yesterday as a gifted athlete and an outgoing team leader. One student compared Fells' enthusiasm and high profile to those of a well-known Washington Redskins player, calling Fells "the Dexter Manley of T.C. Williams."

But T.C. Williams football coach Glenn Furman said that in recent weeks he had heard rumors linking Fells to drugs. Other students who asked not to be identified said that Fells prompted suspicions by driving a late-model sports car and sporting gold chains.

"In the last few months I had heard that maybe Tracy had been around drugs, that he was hanging out with the wrong people," Furman said. "But it was all secondhand, and you can't act on that. I confronted him with it, and everything was denied.

"I'm very saddened by this," he added. "Tracy was going to classes and making progress. We thought he was maturing. People are putting money in front of our young people, and they're making a fatal mistake."

One student who said he is a friend of Fells said, "He had nice clothes, he drove a nice car, and I had seen him around a good amount of money. Sometimes I was a little suspicious."

Furman called Fells the undisputed leader of last fall's T.C. Williams squad, which finished with a 14-0 record, a state championship and a seventh-place ranking in national polls. A 6-foot-2 inch, 243-pound lineman, Fells racked up 100 tackles, 10 quarterback sacks and seven fumble recoveries.

In past years, Furman said, Fells had occasionally been suspended from school for missing classes or fighting, but he said the incidents were minor and unrelated to drugs. Fells had not been suspended during this academic year, Furman said.

Furman said that although Fells' grades were good enough that he expected to graduate with his class this spring, he was enrolled in a course for students with learning disabilities. Fells scored too low on college entrance tests to be eligible for an athletic scholarship at a major college, Furman said, but was being recruited by several small colleges.

"Tracy could bring the team together," said Josh Geiger, a junior center for T.C. Williams. "He could push you when you needed to be pushed, but he could also be your friend. The team respected him."

Eric Moss, a senior soccer player, called Fells "a leader. He's a big person at T.C. Williams. I'm speechless a little bit . . . . I look up to him."

Crockett, the Alexandria police spokeswoman, said Fells was arrested about 2:30 p.m. yesterday by an antidrug unit known as the "jump-out boys." The squad routinely patrols areas of the city where street drug sales take place.

According to Crockett, Fells was sitting in his parked car in the Lynhaven area when a police officer spotted what he suspected was crack inside the vehicle.

Staff writer D'Vera Cohn contributed to this report.