In the end, there's only so much that one man -- for that matter, one organization -- can do.
Based purely on the raw statistics, the 2005 Cleveland Indians were the best team in the major leagues. They might have won 103 games, which would have given them the best record in the American League by a pretty fair margin.
Of course, they did not win 103 games, nor did they win anything else that ultimately mattered. The Indians were, when you add up their raw stats and compare them to their actual record (93-69), the most inefficient team in their league (and just slightly more efficient than the Pirates, the least efficient team in the majors).