It is important to have a viable backup 3B for Youkilis because of two reasons. The first is that he has less than 600 PA so could have an injury of up to 15 games whenever he is injured. Second is that he has a 2 injury rating which means that the injury roll on his card is on a roll of 3 or 11 which comes up more often than the normal 1 injury rating where the injury is on a roll of 2 or 12. You don't need a superstar backup player but Quinlan doesn't cut it IMO offensively or defensively. One of these guys would be better I believe: Luna, Atkins, Nunez, Cintron, Robles or Luis Rodriguez.
Anyway you have to make the final decisions for yourself and be happy with your team. Moves are costly after the season starts when you take a 20% salary hit every time you drop a player. You start the season with an 80M salary cap like everyone else. That goes down if you start cutting players during the season. If you make lots of moves during the season before long you may be down to having only 70M in player salary on your team competing with those teams that made no moves and are still at 80M.