Unbelievably, when a player is "average", that does not mean they're bad. It means average. As in: better than replacement level and fringe level, worse than superstar level and above average level. An "average" player is still worth ~2 WAR, mainly because replacement players are awful and yet still make up most of the minor league population (in terms of skills translating to major league success) which means average players are a valuable commodity.
Applying this information tells us of a difference in classification when dealing with average and replacement levels of talent. Ray Olmedo is a replacement-level infielder. The "average" version of him might be Asdrubal Cabrera. Gabe Gross is an "average" outfielder. Jason Tyner is a poor man's Gabe Gross. This will sound odd, but average talent is still good talent.
Smart teams recognize this and add average players in their cost-controlled seasons, less smart teams pay big money to these same players during free agency. Smart teams realize that fringe level players should be paid as such; others sign Aaron Miles for two years and 4.9 million. Generally though, unless your team is full of superstars (it's not) you can do a lot worse than having average players fill bench slots.
Bumped due to Burrell swamping yesterday.