At the beginning of the 2021 NHL season, many question marks surrounded the Boston Bruins blue line and whether it would be strong enough for another Stanley Cup run. Ultimately, the Bruins backend became plagued with injuries and broke down against a tough Islanders team, losing in 6 games in the 2nd round of the Stanley Cup Playoffs. Now, with the retirement of Kevan Miller and the departure of Jeremy Lauzon to the newly formed Seattle Kraken via the expansion draft, the Bruins yet again face questions regarding their defensemen and more specifically the gap at left defenseman on their second D-pairing. On Wednesday, July 28th, the Bruins will have an opportunity to fill that gap on defense when NHL Free Agency begins. With $20 million in cap space still available for the Bruins after the Taylor Hall deal and General Manager Don Sweeney looking for an all situations D-man, here are five notable left-handed defensemen the Bruins should target in free agency to fill that gap on the back-end.