Coming off their divisional upset win at home over the Titans, the Texans flew to Oakland-Alameda County Coliseum for a Week 16 duel with the Oakland Raiders.  Houston would trail early in the first quarter as Raiders quarterback JaMarcus Russell completed a 20-yard touchdown pass to wide receiver Chaz Schilens.  The Texans would respond with fullback Vonta Leach's 1-yard touchdown run.  However, Oakland responded with kicker Sebastian Janikowski getting a 33-yard and a 30-yard field goal.  Houston would tie the game in the second quarter as kicker Kris Brown got a 53-yard and a 24-yard field goal. In the third quarter, the Raiders scored two unanswered touchdowns: wide receiver Johnnie Lee Higgins caught a 29-yard touchdown pass from Russell, followed by an 80-yard punt return for a touchdown.  The Texans tried to come back in the fourth quarter: Brown nailed a 40-yard field goal, but that was too little, too late.
Question: How many receivers caught a TD for Oakland?
Answer: 2