The Baltimore Colts will learn quickly how much the Lydell Mitchell affair has affected them. They will open at Dallas Monday night, Sept. 4, will take on Miami at home, then will go to New England for a Monday night game Sept. 18.

The Colts traded for running back Don Hardeman of Houston, hoping to get past the first round of the playoffs for the first time under Coach Ted Marchibroda. They have won three straight Eastern Division titles.

The Colts also traded tight end Raymond Chester to the Oakland Raiders, believing No. 1 draft choice Reese McCall from Auburn or veteran Mack Alston can do the job.

The New England Patriots sustained a demoralizing blow when wide receiver Darryl Stingley fractured his neck in an exhibition against Oakland, causing paralysis.

They finished third in the division with a 9-5 record last year. The holdouts of guard John Hannah and tackle Leon Gray, who missed the first three games, were blamed for losses to the New York Jets and Buffalo. Still, quarterback Steve Grogan was sacked only 14 times, fewest in the NFL.

Running back Andy Johnson missed the season with an injured knee, but will rejoin fullback Sam Cunningham this year.

The Miami Dolphins surprised with a 10-4 record, missing a wild card only because Oakland was 11-3 as runnerup in the AFC West.

Miami has rushed for more yards than any other NFL team since 1970 and was second in the AFC in 1977. The Dolphins traded for Delvin Williams of San Francisco, who gained 1,203 yards in 1976 and 934 last season behind a lightly regarded 49ers' offensive line.

Bob Griese wore glasses for the first time and was the league's top passer. The Dolphins sent Freddie Solomon to the 49ers for Williams, but Jimmy Cefalo, third-round draft choice from Penn State, has been showing well behind wide receivers Nat Moore and Duriel Harris.He also returns kicks.

The New York Jets, 3-11 for the third straight season in 1977, are suffering from growing pains under Coach Walt Michaels. They were the youngest team in the AFC, averaging 24.5 years in age and 2.9 in experience. Wide receiver Rich Caster, who will be 30 in December, was traded to Houston for draft choices.

Richard Todd, heir to Joe Namath's job, improved in the early going last year, particularly in a 28-27 loss to Oakland. He injured a knee in November and that hurt his consistency. Tackles Marvin Powell, No. 1 draft pick in 1977, and Chris Ward, No. 1 pick from Ohio State this year, fortify the offensive line.

The Buffalo Bills are starting all over with a new coach, Chuck Knox, and without O. J. Simpson.

The Bills have allowed an average of 340 points the last three seasons. On offense, they passed for more yards than anybody, behind quarterback Joe Ferguson, and Bob Chandler caught more passes than any other wide receiver for the second straight season.

The Bills' No. 1 draft choice was Terry Miller of Oklahoma State. Central Division

The Pittsburgh Steelers won the Central with a 9-5 record, their poorest since 1971. The Steelers will aim for an unprecedented seventh straight playoff appearance and cautious Coach Chuck Noll acknowledges, "We're very optimistic."

Despite playing most of the season with a cast on his broken left wrist, Terry Bradshaw got the Steelers away from overemphasizing running back Franco Harris. Bradshaw led the league with an average of 8.04 yards per passing attempt. Harris still rushed for 1,162 yards.

The Houston Oilers moved themselves up by drafting Heisman Trophy winner Earl Campbell of Texas on the first round. It prompted Coach O. A. (Bum) Phillips to say, "We are looking forward to this season more than any other year since I arrived in 1974."

The holdout of wide receiver-kick returner Billy (White Shoes) Johnson for the first two exhibition games tempered Phillips' optimism. Johnson won the league punt-return title with a 15.4 yard average as the Oilers finished second in the Central with an 8-6 record. He has the highest punt runback average of all time, 13.7 yards.

Bill Johnson, who has an 18-10 record with the Cincinnati Bengals since replacing Paul Brown as coach, may be putting unnecessary pressure on himself when he says, "We drafted well and have youth, speed, depth and talent -- all the ingredients you need for a winning football team."

Wide receiver Isaac Curtis, who missed the second half of last season with a knee problem, is back with Billy Brooks and Pat McInally. The running backs will be the "Ohio State Connection," Archie Griffin and Pete Johnson.

The Cleveland Browns, who have failed five straight seasons to make the playoffs, have a new head coach, Sam Rutigliano. "we'll be more open and have more variety in our offense," he promises.

The Browns got off to a 5-2 start but, after a knee injury to quarterback Brian Sipe, finished 6-8. Running back Greg Pruitt packs a variety of offense on a 5-foot-10, 190-pound frame.

Wide receiver Paul Warfield has retired and Dave Logan will replace him. Ozzie Newsome, wide receiver from Alabama, was drafted on the first round but has been shifted to tight end. Western Division

The Denver Broncos already may have the motivation to repeat as champions of the American Football Conference. Despite a 12-2 record, and two victories in three meetings with Oakland, the preseason consensus is that the Raiders will win the AFC West.

The Denver defense allowed the fewest points in the AFC, 148, and was the NFL's toughest against rushing. The Broncos were 12th in total offense and 14th in passing in the AFC, but had only 17 turnovers. Craig Morton finished second to Griese among AFC passers. Norris Weese has impressed as a nimble, option-play quarterback in exhibitions.

The Oakland Raiders have made it to AFC title games five successive years. Coach John Madden had a 17-game winning streak in 1976-1977.

Quarterback Ken Stabler produced a league-leading 351 points last year.

The San Diego Chargers, who finished third in the division with a 7-7 record, hoped to improve their ranking as the 15th in total offense in the entire league by trading for Lydell Mitchell, who gained more than 1,000 yards rushing the last three years and led the NFL with 71 receptions.

The Chargers sent Joe Washington to Baltimore in the deal, but he had been a reserve running back in 1978 preseason games. He may be missed as a punt returner who had an 81-yard touchdown runback in an exhibition.

Coach Tommy Prothro said before the trade. "We are in the same class" with Denver and Oakland. But the Chargers are said to have a team split over which quarterback should start --Dan Fouts or James Harris.

The Seattle Seahawks' 5-9 record was the best ever for a second-year expansion club and so were the 282 points scored. They have an exciting quarterback in Jim Zorn but he is frequently put on the spot by the defense.

The Seahawks allowed 373 points, most in the league.

The Kansas City Chiefs had the worst record in their history (2-12), a defense that was next to last in 1976 and 1977, and the No. 16 total offense in the NFC last year.

The new head coach is Mary Levy, former assistant to George Allen at Los Angeles (the first time) and at Washington. Levy made the Canadian Football League playoffs in each of his five years as head coach of the Montreal Alouettes, winning two Grey Cups.

He will have a 33-year-old quarterback, Mike Livingston, and a 36-year-old running back, MacArthur Lane.