He spent the past two seasons with the San Francisco 49ers.
Manningham played for the Giants from 2008 to 2011.
Manningham tore his anterior cruciate ligament in 2012. He was limited to six games last season with the 49ers due to the knee problem.
A former third round pick, Manningham caught 160 passes for 2,315 yards and 18 touchdowns with the Giants previously.
In 2010, he caught a career-high 60 passes for 944 yards and nine touchdowns.
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Aaron Wilson covers the Ravens for The Baltimore Sun