Play the Gentle Maiden

Guys are raised to be the knight in shining armor, the prince that rescues the princess. Even if you're a strong tom-boy, sometimes it helps to appeal to that protective nature in most guys. Occasionally find little things that you need help with, that are impersonal enough that you are just asking them as a 'strong male' to help out. Find a jar with a really tight lid and ask him to get it open for you. If your foot feels sore, ask him if you can lean against him just for a second to see what might be wrong. They are little touches to help re-awaken his feeling of protecting you from harm - even as a friend. Once you start getting him to feel protective, you can move forward from there.