How to determine a player's trade value

Here is an interesting question to discuss and debate as we look out the window on these cold winter mornings and count the days until spring arrives: What is the value of a player? When a few people asked me via Twitter yesterday if the Orioles might include Brian Matusz in a potential trade for the Nationals' Michael Morse, it made me wonder about Matusz's - and all players' - trade value. Now I am not proposing the Orioles trade the lefty but you have to wonder how opponents view the soon-to-be 26-year-old lefty right now. Is he a shutdown relief specialist or a starter who once cranked out several quality outings against New York and Boston? It would seem obvious that a good starter has more value than a good reliever, but does a top-notch reliever have more value than a struggling and/or back-of-rotation starter? After his recall from the minors on Aug. 24, Matusz pitched to a 1.35 ERA with a .114 batting average against out of the bullpen. He stranded 14 of 14 inherited runners. By the time the playoffs came, he pitched in all six games the Orioles played and was getting players like Josh Hamilton and Robinson Cano out in critical situations. A player who can do that has to have a lot of value. In determining a player's trade value, what should be most important? Of course talent trumps most, but what about things like service time, current and future salary levels, defensive talent and character? How do teams value different players with splits where one may tear up lefty pitching while a comparable player hits about the same against lefties and righties? What about a player that always has a strong second half? What about a player with terrific postseason stats who exceeds his regular-season production? I ask a lot of questions, but it all has to be considered and different teams may well value the same player differently. Some might put a premium on service time and remaining years of team control. The team's situation also is a clear factor. How does it impact the club to lose a certain player via trade? Are you dealing from a strength or weakening an area that maybe can't afford it? So what do you think?: What should be important in assessing the value of a player in a trade?