2007-08: MacMillan had a disappointing third season in the QJMHL with the Halifax Mooseheads. He suffered a concussion in a Mooseheads' preseason game forcing the physical winger to miss his first NHL training camp with the Anaheim Ducks. Bad luck would strike MacMillan again in November when he was forced to miss six weeks recovering from fatigue. He was able to score 15 goals along with 26 assists and a plus 15 rating while taking 77 PIMs (five fighting majors) in 46 QJMHL games. The Moosehead played deep into the QJMHL playoffs only to be swept in the third round by the Gatineau Olympiques. MacMillan scored three goals with ten assists and a solid plus three rating but taking 20 PIMs in 15 playoff games for Halifax.
2008-09: MacMillan returned late from the Ducks training camp for his fourth QJMHL season with the Mooseheads. The physical winger suffered a knee injury during a practice in late October after a hot start of eight points in nine games. He finally returned to the Moosehead line-up after missing 14 games on December 2, 2008. On December 23, Halifax traded MacMillan to the Rimouski Oceanic for 17-year-old Guillaume Pelletier and four future draft picks in return. He left Halifax having scored four goals along with six assists and terrible minus nine rating in 15 games. The tough winger scored five goals with 16 assists and a plus four rating in 28 games for the Oceanic. The Oceanic managed to make the third round of the QJMHL playoffs only to be swept by the Drummondville Voltigeurs. MacMillan scored three goals (one shorthanded goal) along with three assists and a solid plus four rating in 13 playoff games. His Rimouski team would host the 2008 Memorial Cup but lost in a tie-breaker game against the eventual champions, the Windsor Spitfires. MacMillan only scored one goal while taking nine PIMs including a fighting major in the four Memorial Cup games.
2009-10: MacMillan was assigned to start his rookie professional season with the ECHL Bakersfield Condors as the Ducks had no AHL affiliate. He scored two goals along with four assists and a minus four rating while taking 20 PIMs (two fighting majors) in 30 ECHL games. MacMillan was arrested on a DUI and driving without a driver's license charges while out of the line-up with back spasms in early January. The rookie forward was sent home by the Ducks for personal reasons only to return on loan to the injury ridden Abbottsford Heat for the last seven games of the AHL season. He would only contribute seven penalties minutes which included a fighting major. The Calgary Flames acquired MacMillan in a trade with the Anaheim Ducks on July 1, 2010 for Jeffrey Jaffray.
2010-11: MacMillan had a tough rookie season with the AHL Heat, being a healthy scratch at times while playing only 55 games this year with Abbottsford. The 21-year-old was only able to score five goals along with six assists which was definitely not a solid offensive year. The versatile forward plays a physical two-way game but struggled to show the Heat coaches his defensive side when he finished the season with a minus 13 rating. The strong, aggressive winger showed a willingness to drop the gloves to stand up for teammates on four occasions but only accumulated a total of 32 PIMs for the season.
MacMillan plays a physical fore-checking game but needs to concentrate on his offensive skills while show his strong two-way game. He needs to regain his confidence to play well at this level for an entire season and prove that the change of scenery was the right move for him. The former number one draft choice should definitely leave the fighting to others and show his skills instead.
MacMillan will most likely be assigned to the AHL Abbottsford Heat for the entire season where he probably will play on one of the bottom two forward lines. The physical forward will need to remain healthy and bring more offensive to his game to show the Flames that he can play at the professional level.