THE SIDELINES : Patrick McEnroe in Semifinals

Patrick McEnroe, John’s younger brother, further polished his reputation as a doubles player today when he and partner Jim Grabb advanced to the semifinals of the Masters tournament.

The two Americans completed their perfect record in the preliminary matches by defeating Australians Darren Cahill and Mark Kratzmann 7-6, 6-1, 6-4.

Cahill and Kratzmann also qualified for the semifinals despite the loss, having won their previous two matches. The other two sets of semifinalists were to be determined tonight.

McEnroe, at 23 seven years younger than his more famous brother, and Grabb won the French Open title in July on their way to earning more than $183,000 this season.

The way they beat defending champions Jim Pugh and Rick Leach in their first match of the Masters tournament, and then crushed Pete Sampras and Jim Courier to reach the semifinals, showed doubles teamwork at its best.