When Eddie joins the 118 in "Under Pressure," Buck immediately acts coldly towards him because he feels threatened by Eddie's presence as well as how quickly and seamlessly he becomes a part of the team. This hostility is short-lived, however as the two bond over a dangerous situation that involves taking a live bullet out of a 911 caller's leg. Once the bullet is safely obtained, Eddie commends Buck for being "a bad-ass under pressure" and they vow to have each other's back which effectively consolidates the beginning of their friendship. From then on, Buck and Eddie work together harmoniously while on the job. They also support one another outside of it. Buck introduces Eddie to Carla when he finds out that Eddie is struggling to find some permanent help in taking care of his son, Christopher who was born with cerebral palsy and Eddie confides in Buck about the dilemma he faces with letting his estranged wife, Shannon back into Christopher's life.

As a result of such events, their relationship becomes stronger to the point where Buck views Eddie as his best friend. He mentions this in "The Searchers" as he panics to find Christopher in the aftermath of the tsunami and worries about how he's going to "tell his best friend that he lost his son." Once Christopher is found, safe and sound, Buck is plagued by the guilt of having lost him in the first place but Eddie quiets his erratic thinking by telling Buck that he saved Christopher and that "there's nobody in this world" he trusts with his son more than Buck.

Although the events of the lawsuit create a divide in their relationship by pitting the two against each other, they are quickly able to overcome it and reconcile in "Monsters." Eddie accepts that while Buck's methods of returning to the job were unorthodox, it was never his intention to hurt anyone and Buck realizes that his actions can greatly impact those around him. Even with this reconciliation, Buck notices that there is still "something going on" with Eddie in "Malfunction" which he later discovers to be Eddie's unhealthy coping mechanism of street-fighting.

When Eddie is required to attend therapy sessions after Bobby finds out about his street-fighting, Buck stands by his best friend and supports him wholeheartedly. In "Fallout," Buck invites Eddie and Christopher to his apartment for a night of pizza and video games. This seems to comfort Eddie who confides in Buck that traditional therapy might not be for him and that he is finding it difficult to "click" with his therapist, Frank. Later, Eddie adds that spending a quiet night in with Buck and Christopher and beating Buck at video games is more like "his kind of therapy."

Buck continues to be there for Eddie in "Christmas Spirit" when Eddie mentions how Christopher is disappointed that they won't be able to spend Christmas together since Buck, Eddie and the rest of the 118 are scheduled to work on Christmas day. Buck makes it possible for Eddie to be with both Christopher and his grandmother by bringing the Christmas celebrations to the firehouse with Athena's help, effectively proving how much Buck has grown to care about Eddie and the lengths that he will resort to in order to ensure that both Christopher and Eddie are happy.