According to Deadline, the first director attached to "The Gray Man" was James Gray ("Ad Astra," "We Own the Night"), but that was way back in 2011. In 2015, Deadline also reported that Joe and Anthony Russo of Marvel Studios fame were attached to direct, but they dropped out of that and opted to write the script. The brothers were apparently overwhelmed with their Phase 3 projects for the MCU, so taking on "The Gray Man" was too much at the time.
Since the project took several more years to get going, the Russo brothers were able to hop back aboard as directors officially in 2020 (via Deadline). The Russo's production company AGBO is also behind "The Gray Man," with Joe Russo getting the screenplay credit alongside "Avengers: Infinity War" and "Avengers: Endgame" writers Stephen McFeely and Christopher Markus.
In a conversation with Fandango's Erik Davis (per Syfy Wire), Joe Russo amped up his new movie, saying, "I feel like 'The Gray Man' is basically everything we learned over the last decade poured into one film." In the last 10 years, the Russo's have directed some of the biggest movies ever made, including the final two "Avengers" flicks, "Captain America: The Winter Soldier" and "Captain America: Civil War." If they're carrying lessons that they learned from those films, "The Gray Man" shouldn't be anything less than stellar.