I am sure the Broncos explored trade options.  Teams did not want to give up a draft pick for Ward because he is an older player in the last year of his contract.
You mentioned yourself that Ward will have 6 to 8 phone calls by noon.  If another team desperately wanted him, they would have given Denver a 7th round pick for Ward.  That way they would not have to compete with other teams in the open market. And have Ward for 1 year at a reasonable cost ($4.5 Million).  Now, teams not only have to compete against each other but also have to pay maybe more for his services. 
The conclusion is no team thought that Ward was worth even a 7th round pick.  Or maybe the Broncos did Ward a solid by releasing him (as opposed to trading him to the Jags for a 7th round pick).  This way Ward (as a respected veteran Bronco) can pick his own team of choice.