As the summer doldrums enveloped most of the new business, Sports Illustrated managed to unleash two crackerjack three-part series in the past two months: First on big bucks in professional athletics; then on legalized brutality in football.

John Underwood's football trilogy, which concluded in the Aug. 28 issue, is a certified eye-widener, from an opening observation that about 1 million high school players will be injured this fall, to an analysis of the football helmet as headly weapon, to the pyschological strategy involved in taking out the quarterback on every play.

The most garish material appears in part three, where Underwood quotes at length a former San Diego Charger's locker-room analyst who says he watched amphetamines turn the team into a squad of raging brutes.

"The second time I went through the tunnel to the field," says Dr. Arnold Mandell, a pioneer in brain chemistry research, "I accidentally hit the elbow of an offensive tackle I knew pretty well - a bright guy, a nice guy. He banged me into the wall, really unloaded on me. Later he apologized. That year we played at Houston, and one of the sweetest guys on the defensive teams - I'll never forget - was literally drooling . . .

"Amphetamines in large doses produce a paranoid psychosis. That means the guy doing the damage actually thinks the other guy is out to get him. It's Good Guys versus Bad Guys. The quarterback, as head of the opposition, is the Number One Bad Guy. It's open season on him. I laugh when NFL players talk about the dangers of synthetic turf and helmets, and all the while they're permitting amphetamine-crazed athletes to go on the field and assault their quarterbacks."

A nation that has spawned serious drinkers such as Fitzgerald and Hemingway may be surprised to find that most of the 50-odd writers queried by the October Writer's Digest consider themselves light boozers, with a heavy preferenec for - Faulkner will turn in his grave - White Wine .

There are exceptions. John Ciardi calls himself a heavy drinker. "I drink in company, moderately. Come 2 to 4 a.m. when I leave my desk I can't get to sleep. If I happen to have a Seconal, that will put me to sleep. But my MD won't give and I must swozzle my insomnia with bourbon. Trouble is I can drink most or all of a fifth then and still not be sleepy."

Joseph Wambaugh, however, says he won't drink with writers. "Prefer the company of cops," he says. "If none around I hang out with whores, plumps and thugs, which is why I'm in the movie business."

Wilfred Sheed notes that "the middle-aged drunk is the quintessential American and we have to keep in touch with the fellow. Drinking is the only way to get him to talk."