The average time for a college third baseman to make it to the majors is 3.88 years. The average for a high school third baseman is 4.92 years. This time can be reduced if a player has a higher skill level. Elite players only take 2.9 years out of college and 3.92 out of high school. These are just averages. Third baseman are often impact bats that tend to move across the diamond at some point. They usually have the arm to move to RF and will move there if they are athletic.
Using stats from 2009-2013, here are the positional averages.
This is to give perspective on how many MLB players come from each age group. I hope it shows how amazing even backup players are. You have to be a special player to make it to the majors and the best of the best to be good. Most ages only have 2 or 3 starter caliber players. It shows how much of a success it is for a team to develop a player to get them to the majors.