If Howard University was to play its opening football game today, two players not even listed On the roster or depth chart would start in the offensive backfield.

Donald Canada, a transfer from Santa Monica (Calif.) Junior College, and Wesley Lewis, a freshman from Sarasota, Fla, turned in near-flawless performances and sparked the White (varsity) team to a 37-0 show over the Blue (reserve) unit in yesterday's final intrasquad scrimmage.

Howard opens its season Sept. 16 against Mayland-Eastern Shore.

"Both Canada and Lewis have played well in preseason," said Coach Doug Porter, "and right now are the starters in the backfield."

Lewis, a 5 foot 9, 175-pound speed-stef, rushed through a generous second-team defense for 43 years on five carries. He scored once, on a 24-yard burst. Canada, who used his 5-10, 205 pound muscular frame to clear out paths for his running mate, added 21 yards on five carries.

Gary Madden (48 yards on seven carries) and Cornelius Quarrels (29 yards on six carries) also were impressive. Rugby Practices Set

Practices for the Washington Rugby Football Club, which will include Philadelphia, New York and Boston teams among its opponents this season, will be held each Tuesday, Wednesday and Thursday evenings at 6, on the field across from the Lincoln Memorial along the Reflecting Pool.

"Our offense is much farther along than it was a year ago at this time," said Porter. "We've had to devote more times to our offense because of our youth. We've emphasized our running game especially, and I was pleased we had fewer missed assignments.

"It will be hard to keep that competititive edge for two more weeks. The fellows want to play. We got a good chance to see everybody, especially our reserve defensive players. We're going to need them during the season and we want them to get in as much work as possible."

The starting defensive unit, which played only 20 plays, was not sharp, giving up big chunks of yardage, yet holding the reserves scoreless.

The reserve defensive unit was victimized by the running of Lewis and Co., the passing of Raymond Gray and Brian Thomas and the receiving of Steve Wilson and Greg Scott.

Scott (five receptions, 97 yards) scored the first two touchdowns on Gray passes of 36 and 14 yards. Wilson (four receptions, 83 yards) had the longest play of the day, a 56-yard passrun on which he spun out of a tackle and barreled over a defender into the end zone.

Starting from its 30-yard line, the first offensive unit drove for scores three consecutive times on seven, six and four plays, respectively.

Porter was not as concerned over the lack of tenacity and concentration of his defense as he was over the number senseless penalties.

"That was one of our major problems last year. A holding or an interference call, we can deal with, but there are no excuses for late hits and personal fouls," he said.

One othe bright spot was the place kicking of Howard Ward. The sophomore connected on four of four extra-point attempt and kicked a 45-yard field goal to end the two-hour scrimmage.

There were no injuries reported and only center Timothy Lee (strained knee ligaments) was held out.