Negotiations have already begun between City chiefs and Sawyer's representatives but Coppell wants to wait until the start of pre-season training before settling on his squad.
Coppell told the Evening Post: "The talks haven't really progressed because I want to make an assessment before I act. In an ideal world, I will know everyone who is available and then get to know the players after they report back on July 1.
"I can look at so many DVDs of games, but it is only when I see a player train that I can see what makes him tick and how he might fit in. Only when you see that, can you start making decisions."
Sawyer, who spent a month on loan with the Robins towards the end of the season, has been released by Plymouth.