First, let's compare Cardinals wide receiver stats over the last three years.
Larry Fitzgerald: 330 receptions, 4,544 yards, 34 TDs
Anquan Boldin: 413 receptions, 5,458 yards, 29 TDs
Now, let's compare salaries over the next three years (these are approximate, and via Pro Football Talk):
2008: $10 million
2009: $10 million
2010: $10 million
2008: $2.5 million
2009: $2.75 million
2010: $3 million
Presented in that light, one could certainly understand if Anquan wasn't too happy about his financial situation.
If the guy in the cubicle next to yours was doing the same job you were, and you were (arguably) doing it better, yet he was making three times what you were making, you might like for that situation to be rectified, yes?
To my knowledge, Boldin hasn't made any public noise about being unhappy (and he probably won't; he's a good soldier), but if he hadn't expressed any displeasure at least privately, then he's just not paying attention.
He might put up with being relatively underpaid for one year, but I doubt he'll be willing to do it any longer than that.
• Anquan Boltin'? / Pro Football Talk?