Ravens sign Joe Flacco to three-year extension

— -- Baltimore Ravens quarterback Joe Flacco signed a three-year extension with the team on Wednesday that puts him under contract through 2021.

The team didn't announce terms, but a source told ESPN's Adam Caplan that the deal is worth $66.4 million with $44 million fully guaranteed ($40 million in a signing bonus and a $4 million base salary in Year 1). The deal is expected to free up much-needed space under the salary cap for Baltimore.

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. Flacco's contract presented a major opportunity for Baltimore to create cap space.

By giving Baltimore more cap space, Flacco is expected to receive more guaranteed money than what he was 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's Adam Caplan and Jamison Hensley contributed to this report.