The Chicago Cubs, who have been a disappointment all year to General Manager Dallas Green, had a 15-day stretch in August during which their starters (2.77) and their relievers (1.50) had superb earned-run averages. Nevertheless, Green, in an attempt to speed up his five-year plan, is expected to go into the free agent market this winter for at least two players. ''While I'm not really in favor of building through free agents,'' Dallas explained, ''the best kids in our farm system are probably a couple of years away.'' Green's priority is pitching.
The Cubs, in a first for them, have retired the No. 14 uniform of Hall of Famer Ernie Banks. Among Ernie's more impressive statistics: 512 career home runs; two National League Most Valuable Player awards (1958 and 1959); and 13 All-Star Game selections. Banks, a guest at the Los Angeles Dodgers Oldtimers Luncheon, still looks as though he could play a doubleheader. Originally a fine shortstop, Ernie finished up as the Cubs' first baseman.