Carlos Silva pitched himself off the Cubs roster. Carlos is an interesting pitcher, as he gets poor results despite showing great control. His main problem was that his fastball got hammered, with opponents hitting .400 against that pitch. The explanation shows that he might have depended too much on his control.
You can see his control in this heat map of his pitch frequency:
Now look at the plot in terms of release velocity:
When Carlos throws fast, his pitches miss the strike zone. So batters get strikes that are in the mid 80s in general. If we take this plot down to just his fastballs:
The same thing happens. His fastest pitches are out of the strike zone. Most major league batters can hit a fastball, and all of them can hit a slower one in the strike zone. Carlos looks like he took velocity off his pitches to get strikes, but they were strikes batters could handle easily.