The Boston Celtics appear to be on the verge of adding veteran shooting guard Jason Terry to their roster for the coming season.

Terry is a soon to be 35-year-old free agent formerly of the Dallas Mavericks. He is expected to fill the Celtics' mid-level exception and sign a three year $35 million dael. With Avery Bradley already penciled in as the team's starting shooting guard, Terry is expected to fill the sixth man role which he did so well with the Mavericks.

As a former sixth man of the year winner, the Celtics will expect Terry to fill what was a massive need for them last season. Despite some upstart performances from Mikael Pietrus and Keyon Dooling in spurts and Ray Allen's presence at times from the bench, the Celtics primarily had to rely on their five starters to put the ball in the basket last year.

Terry offers them a player who can do that in multiple ways while also being a proven clutch performer who won't be scared to take the big shot at the end of games. While Paul Pierce is a proven clutch performer already on the roster, having a second option like him significantly improves the offense.

Unlike Pierce, Terry is still a very athletic player who doesn't have to rely solely on his outside shot to score.

Initially, this move seemed to be a direct response to Ray Allen's scheduled meetings with the Los Angeles Clippers and Miami Heat. The Heat and Clippers will be very tempting to Allen because both possess quality rosters capable of challenging for a championship this season.

However the Celtics believe that they also possess a roster capable of winning now despite a season seen as a prelude to a rebuilding process last year. The Celtics still want to re-sign Allen and were believed to have doubled the Heat's $6 million two year contract initially to retain him.

Bringing Allen back would give the Celtics two excellent scoring options from the bench. Depth is going to be key for the Celtics if they are to challenge again next season. Potentially, they could have a bench with Keyon Dooling, Allen, Terry, Jeff Green/Brandon Bass, Jared Sullinger, Fab Melo, Jajuan Johnson and Greg Stiemsma.

Obviously some of those players are not currently with the team, but they are expected to be Celtics if all goes to plan. In that situation, the Celtics can conceivably go nine or 10 deep in the playoffs. Complementing the starting unit with different types of players is important for the Celtics because they cannot rely on their key players for 40+ minutes every night anymore.

With the flexibility to surround Rajon Rondo with shooters, in a lineup featuring Allen, Terry, Pierce and Garnett, or the ability to go big with Rondo, Bradley, Green, Sullinger and Melo.

Adding Terry and bringing back Ray Allen would give the roster more veteran options to pair with their suddenly athletic roster. Even if Allen isn't re-signed, Terry gives the team an excellent bench presence to aid their attempts to return to the playoffs this year.

Cian Fahey writes for the Guardian, Steelersdepot and FFBLife. You can find him on twitter @Cianaf