Couples, who will captain the American team at the Presidents Cup matches this month, and Haas, who will be an assistant captain, both shot a 3-under 68 in the opening round at the rain-soaked TPC-Harding Park course.
Rain fell off and on during the first round and at times pelted down on the elite 30-player field.
Couples birdied five holes on the front nine and then hung on as the heaviest of the rains began to fall.
Lehman began the tournament in first place in the race for the Charles Schwab Cup, which will be decided this week and will go to the yearlong points leader. Lehman has a 382-point lead over Mark Calcavecchia in the chase for the $1 million top prize.
Lehman was tied for fifth at 1-under 70 with Kenny Perry and Rod Spittle. Calcavecchia and Senior both had a 71, Cook shot a 73 and Cochran fired a 74.