Place chicken in resealable plastic bag. Mix together soy sauce, lime juice, Worcestershire sauce, garlic and mustard. Reserve 1/4 cup marinade. Pour remainder over chicken in bag. Toss to coat well. Marinate in refrigerator 30 minutes or up to 4 hours. Drain chicken; discard leftover marinade. Sprinkle chicken with pepper.
Spray large nonstick skillet with butter-flavored cooking spray and heat over medium. Add chicken and cook about 6 minutes on each side or until done (internal temp 170°F).