Rollerball

Jonathan E. (James Caan) is the veteran star of the Houston rollerball team. By virtue of his stellar performance over the years, he has become the sport's most recognizable player. After another impressive performance, Mr. Bartholomew (John Houseman), chairman of the Energy Corporation, announces that they will feature Jonathan in a "multivision" special about his career.
Bartholomew tells Jonathan that they want him to retire. He offers a lavish retirement package if Jonathon so announces during the special, while emphasizing the benefits of corporate-run society and the importance of respecting executive decisions, never explaining why he must retire. Jonathon struggles to understand why while thinking about his former wife Ella (Maud Adams), who was suddenly given to an executive.
Jonathan later tries to access books but finds they have been classified, transcribed, and stored in a corporate computer bank. He comforts himself back at his ranch by watching a video of his ex-wife, soon discovering that Energy Corporation has sent him a concubine.
Rollerball soon degrades into senseless violence; the rules are made more dangerous in order to force Jonathan out. The semi-final game against Tokyo will be played with no penalties and limited player substitutions, yet Jonathan refuses to yield, intending to play. A Houston instructor (Robert Ito) insists on teaching the team how to counter Tokyo's unorthodox martial arts skills, but they simply drown him out with multiple chants of "Houston"! The brutality of that match kills several players, including Houston's lead biker; it leaves Jonathan's best friend and teammate Moonpie (John Beck) in a brain-dead vegetative state.
The corporations hold an emergency meeting to discuss Jonathan's obstinate refusal to retire, deciding that the championship game against New York will be played without penalties, player substitutions, or a time-limit, in the hope that Jonathan will be killed. The executives' meeting reveals that rollerball was conceived not merely to satisfy man's blood lust but to demonstrate the futility of individualism. Jonathan's talent and longevity is threatening that purpose. Before the match, Jonathan has a surprise visit from his ex-wife, Ella, who reveals that the corporations ordered her to convince him to retire.
Jonathan decides to play, and the rollerball Final quickly loses all semblance of order as players are incapacitated or killed. The crowd, raucous and energetic at the beginning, gradually become more and more subdued as the carnage builds, finally becoming a gladiatorial contest. Jonathan is the last Houston player, while two remain from New York. After a violent struggle directly in front of Mr. Bartholomew, Jonathan dispatches one, grabs the steel ball, and threatens the remaining New York player; the world watches in utter silence. With a moment's pause, Jonathan releases him, gets to his feet,and because it's what he does, he painfully makes his way to the goal, scoring the game's only point: Houston 1, New York 0.
Jonathan begins to freely skate around the track in silent victory, and the coaches and fans of both teams start chanting, "Jon-a-than"! They do so first in a whisper, then in voices which grow louder and louder as Jonathan continues around the track. Mr. Bartholomew hurries to the arena exit, knowing that Jonathan E. has defeated the purpose of the game. As the cheering becomes a roar, there is a freeze frame hold on Jonathan's blurred face, over which is played Bach's iconic prelude to Toccata and Fugue in D minor, as the film credits roll.

Question: Who is Jonathans' best friend?
Answer: Moonpie