Tort and Contract are alternative explanations of differing duties.  In tort, the duty arises simply from the agreement to perform, and then failing to heed the standard of care, with damages.  In contract, the dury arises from an agreement to perform certain specific tasks.  As an example, the agreement to prosecute an appeal.  when that does not get done, there is both a tort and a contract cause of action.  Here is an article discussing these principals in an Arizona context.