I've seen a lot of instances where on the first few days (don't know how many for certain, guessing 5 or so), players are much pickier than they are once the first days have happened. I had a guy I wanted to sign, he was the perfect fit for my team, but he didn't like my organization.
I checked him every day and suddenly, he was interested in signing with me. I did manage to win the bidding war on him and he did sign. But then again, this was a solo league where I could look EVERY day and in an online league, there is a chance the guy would sign before you had the chance of offering him a contract.
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-Chris
TWIB - Commish - Cleveland (1884 - present)
MCBL - Commish - 50, 55, 59, 65, & 68 World Champion New York Yankees
NTBL - Commish - Chicago Cubs (1918 - present)