Ravens, Joe Flacco agree on three-year extension

— -- The Baltimore Ravens and quarterback Joe Flacco have agreed in principle to a three-year contract extension through 2021, a source told ESPN's Adam Caplan.

The Ravens were looking to lower Flacco's $28.55 million cap number, which is the third-highest in the NFL, before the start of free agency on March 9. This is the best move for Baltimore to create cap space.

By giving Baltimore more cap space, Flacco is expected to receive more guaranteed money than what he is scheduled to earn over the final three years of his current deal ($58.6 million) and continue to average more than $20 million per season.

The Ravens had just $2,867,494 in cap space as of Wednesday and recently placed the franchise tag on kicker Justin Tucker (worth $4.5 million).

The Ravens have two key starters set to enter free agency -- offensive lineman Kelechi Osemele and linebacker Courtney Upshaw -- and could use the cap space to try to re-sign both.

ESPN Ravens reporter Jamison Hensley contributed to this report.