The 30 major league clubs usually put many of their players through waivers in August as a formality. It's a way for general managers to have flexibility just in case a trade possibility comes up later in August. They also sometimes want to shed payroll, as was the case last year, when the Giants claimed Cody Ross from the Florida Marlins. Rather than pull him back or work out a trade, the Marlins decided to let the Giants simply take on the rest of Ross' $4.45 million salary.
August transactions have certain stipulations. Should another team or teams claim a player, the team he plays for can do one of two things: It can pull the player back, ending the ability to trade him. Or, if the team sees a trade match with the claiming club, an immediate phone call is in order to gauge whether that club has sincere interest.
Many teams will just claim a player to “block” that player from being claimed, then traded, to a rival team or one contending with them. (Waiver claims always work in reverse order of current standings.) If there is interest, both sides have 72 hours to work out a deal.
When I was a GM, it was usually pretty obvious which players would clear waivers. Although there have been surprises throughout the years, just two appeared to be blunders at the time. The first was in 1998, when then-Padres GM Kevin Towers put in a claim for Randy Myers with the intention of blocking the competing Atlanta Braves from trading for him. The Blue Jays instead let the Padres have him on the waiver claim and the two years and approximately $12 million left on his contract.