You can replace it if you wish. Grilled chicken, Pan fried chickenor Baked chicken breast.
Anchovy paste really adds to the classic Caesar Caesar saucebut Worcestershire sauce will work too (or Worcestershire substitute). If all you can find are whole anchovy fillets, blend 2 anchovy fillets to make 1 teaspoon of anchovy paste. Remember that anchovy paste has vinegar and spices added to it, and is milder in flavor.
Add different types of proteins to this salad to make it suitable for different diets, such as: Canned chickpeas, Baked salmonor Fried shrimps. For vegans use Vegan Caesar Dressing.