The U.S. Tennis Association computer has digested performances Oct. 1, 1977-Sept. 30, 1978, and the No. 1 male player in the world is - Jimmy Connors. Jimbo tallied 16.937 points to 16.131 for the other claimant, Bjorn Borg. From them, a long drop to No 3 Vitas Gerulaitis, 11.822 . . . Annandale, Madison and West Springfield, the Northern Virginia schools taking 10-0 records into the regional football playoffs, rank 2-3-4 statewide under Group AAA ranking system - behind Hot Springs, 10-0 with a 307-22 scoring differential . . .The Marines hasten to inform that the listing of leaders in Sunday's marathon omitted George Marien-thal, 156th in 2:49:46 - and we mean hasten. He's assistant secretary of defense. The young entrant pictured on Page A1 of Monday's Post turns out to be Casey Beathard, 12, and the photographer didn't even know he was the son of Redskin General Manager Bobby Beathard. Where'd Casey finish? At the finish line, and said papa Beathard, "one place ahead of me" . . . Donnie Allison, the stock car ace, didn't find out until yesterday that his protest had availed and he was awarded first in Sunday's Dixie 500, one place ahead of Richard Petty. A miscount of Allison's laps led to hours of argument and review Sunday night and Allison went to bed thinking Petty, originally declared victor, had been upheld. Not so.