Chet Moeller, U.S. Naval academy class of '76 -- what, already finished his military obligation? we wondered while duty reporting his signing with the NFL's New York Giants the other day. Now we learn why: medical discharge a year early.

Diabetes, discovered in February. But Moeller, 26, won't let that stop him in a bid for football success, next chapter.

A jarring hitter as rover back earning All-America stature in the Navy defensive secondary, Moeller went on to serve almost four years in the Marines. Based in Norfolk, he was in computer sciences. His illness stripped 20 pounds from his 185-pound frame, but he has gained it back, and with an insulin shot each morning, functions normally.

Now, if he functions back to his 1975 form -- well, Syracuse Coach Frank Maloney (who sent along Redskin No. 1 draft pick Art Monk from his 1979 crop) said that the two best players he saw that year were Maryland's Randy White and Navy's Moeller. We all know about White and Dallas and Super Bowl MVPs.Can Moeller become the sixth man out of Annapolis or West Point to make it in the big league?

Sic transit -- . . . Jacinto Vazquez, rose-bedecked and not a little richer after riding Genuine Risk in the Kentucky Derby on Saturday, may be out of the Preakness even if the filly from Loudoun County runs in the May 17 Baltimore classic. Vasquez was thrown from his mount in yesterday's Aqueduct feature and hospitalized with what was suspected to be a fracture of the left hand.

It was May 12, 1961, that Tony Bettenhausen Sr. perished during a practice run at Indianapolis Motor Speedway. Yesterday, rookie Tony Bettenhausen Jr., in practice for the May 25 renewal of the Indy 500, lost control in the south short chute going into turn two, slid sideways 560 feet, completed a half spin, slid another 240 feet and wham, hit the wall. Happy ending, semi, anyway: only scrapes and bruises . . .

Off again, on again: Aqua Velva's $1,000-per-game payoff for the season's longest hitting streak in the majors -- which we last week reported off -- has the green light again, Commissioner Bowie Kuhn evidently easing the opposition to this type of incentive bonus for players. Now, if Pete Rose expects to have the longest streak for the third successive year, he has some snapping out to do. Through last night's action, Rose was mired at .203 . . .

Social note, a real sporty wedding coming up May 16, St. Catherine Laboure Church in Wheaton: Patty Davis, daughter of Redskin alumnus Andy Davis, and Jay Gallagher, former Mount St. Mary's basketball star and son of St. John's High Coach Joe Gallagher . . .

Flash review of NFL Films' Redskins 1979 highlights flick (premiered at Redskin Alumni pregolf gathering), runs about 27 minutes, available to organizations by request via Redskin Park: Not bad, but still a lousy ending in Dallas.