After reaching the final of the $400,000 Volvo Grand Prix Masters tennis tournament today with a formidable display of power tennis, Ivan Lendl denied charges that he stopped trying in the second set of an inconsequential round-robin match against Jimmy Connors Friday night at Madison Square Garden.

"I am a professional tennis player and I am trying every match," he said but skeptics remained unconvinced.

Connors beat Lendl, 7-6, 6-1, in a match that did not end until 20 minutes after midnight this morning, then accused the 20-year-old Czech of not trying in the second set, criticized him bitterly, and called him "a chicken."

Both players already had qualified for the semifinals of the Masters with 2-0 round-robin records, but the pairings hinged on the outcome. Since Bjorn Borg, fatigued and drained by an exhausting victory over John McEnroe late the previous night, had lost to Gene Mayer, 6-0, 6-3, on Friday afternoon, Connors and Lendl both knew that loser of their match would play Mayer at 1 p.m. today, and the winner would play Borg afterwards.

Given those circumstances, the result of an unfortunate flaw in the hybrid round-robin-knockout Masters format, there was every temptation for a player to deliberately lose, and play Mayer rather than Borg. Since the loser would be due back on court in less than 13 hours, there was also incentive for the man who lost the first set to lose the second quickly.

The first set was good and competitive. Lendl had set points at 30-40 on Connors' serve in the ninth and 11th games, but lost the set in a tie breaker, 7-1. He then abandoned his base-line game and started rushing the net suicidally, winning only 10 points in a seond set that was over in just 18 minutes.

It certainly appeared to most witnesses that Lendl was throwing the match, and Connors was sure of it.He gestured disdainfully at Lendl, and later blasted him on a cable television interview and at a press conference.

"I think he's a chicken. No matter what happens, you're supposed to try your hardest on every point," said Connors, a pro who always tries his guts out.

Asked his reaction to Connors calling him "a chicken," Lendl said: "That can be his opinion. If he thinks I didn't try, it is better that he says that, and doesn't say he thinks I tried. It is his opinion. Everybody is entitled to his opinion . . . I understand how somebody can say I did, but I say I didn't."