Foote, 28, who team sources confirmed to ESPN.com would be released after the minicamp, is in the final year of a contract in which he is expected to make $2.89 million.
Steelers coach Mike Tomlin said the team will not fine Foote.
"He and I agreed mutually that it was best for all parties involved for him not to be here this weekend," Foote said.
It had been rumored for much of the offseason that Foote, made extraneous by the emergence of two-year veteran and former first-round pick Lawrence Timmons, would be traded or released. It is believed the Steelers attempted to trade Foote during the NFL draft last weekend.
A former fourth-round pick in 2002, Foote started all 16 games for Pittsburgh and recorded 86 tackles and 1.5 sacks last season.
"Whatever he decides to do, we're going to support him," Steelers receiver and team captain Hines Ward said after Friday's practice. "But Larry is a vital player, a great player and he helped us win two Super Bowls. So I'll be sad to see him go."
McDonald was a fourth-round pick by the Rams in 2003 before signing with the Lions in 2007. He led Detroit with 79 catches for 943 yards and six touchdowns that season and had 35 catches and one touchdown last season.
Ratliff was a second-round pick by the Bengals in 2004 before spending part of the 2007 and 2008 seasons with the Colts.
The Steelers annually bring in a kicker and punter to compete with their starters during training camp, and will do so again after signing Johnson and kicker Piotr Czech.
Johnson averaged 41.8 yards on 40 punts last season before being cut by Arizona in December. He has punted for the Saints, Eagles, Bears and Cardinals since 2002. Czech, from Wagner College, went to training camp with the Ravens last season but was cut.
The Steelers also signed wide receiver Jayson Foster, who spent time on their practice squad last season. They cut long snapper Jared Retkofsky, who signed after starter Greg Warren injured a knee at midseason last year.
James Walker covers the AFC North for ESPN.com. Information from ESPN.com's Len Pasquarelli and The Associated Press was used in this report.