It was a case of old versus new at sunny Withdean on Saturday as Albion went for a hat-trick of victories for the first time since April.
Dave Beasant, 44 next month, was back between the posts for the Seagulls while the Millwall substitutes included 15-year-old Moses Ashikodi.
Beasant, fit again following a bout of food poisoning, returned for his third appearance for the club.
Ben Roberts went back to Charlton on Monday after completing his month on loan in last Saturday's 1-0 triumph at Bradford.
Boss Steve Coppell was forced into one other change, Graham Barrett earning a recall up front in place of the banned Gary Hart.
Barrett, bidding to end a 15-game goal drought, got the nod ahead of new loan signing Tony Rougier from Reading.
The 31-year-old Trinidad and Tobago International started life with the Seagulls as a substitute.
Ivar Ingimarsson, on loan from Wolves, made his home debut at the heart of the defence.
Ingimarsson scored on his previous appearance at Withdean last season to help Coppell's Brentford to victory.
Nathan Jones, missing for the last two matches with an ankle problem, joined Rougier on the bench at the expense of Guy Butters.
Ashikodi, an England Under-16 International of Nigerian descent, was in the Millwall squad because they were still without nine players through injury or illness.
The absentees included Dennis Wise, former Albion triallist Andy Roberts and Burgess Hill-based defender Matt Lawrence.
Brighton-born Albion fan Paul Ifill returned from a one-match suspension for the visitors.
The Lions also welcomed back striker Neil Harris from a long-term ankle injury.
Steve Gritt received a reception as warm as the sunshine as he made his way to the Millwall dugout.
Mark McGhee's No. 2 is fondly remembered by Albion fans for steering the Seagulls to Football League survival with a last day draw at Hereford six years ago.
Albion: Dave Beasant; Paul Watson, Kerry Mayo, Danny Cullip, Dean Blackwell, Paul Brooker, Richard Carpenter, Ivar Ingimarsson, Bobby Zamora, Graham Barrett, Simon Rodger. Subs: Oatway, Jones, Packham, Piercy, Rougier.
Millwall: Tony Warner; Robbie Ryan, Paul Ifill, David Livermore, Neil Harris, Steven Reid, Darren Ward, Alan Dunne, Charley Hearn, Paul Robinson, Steve Claridge. Subs: Gueret, Ashikodi, Kinet, Bull, Rees.
Referee: Mr A. Leake (Lancashire).
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