Just as he did against Norwich in the first Championship game of the season, Langstaff came off the bench to score in the final 10 minutes of normal time and secure a 2-1 win for Millwall.
The former Notts County striker has had a tough time of it at The Den since joining the club 18 months ago, scoring just once in his first season and netting only three goals in total from 51 league appearances.
He came on with his side firmly under the cosh against Bristol City, having had just two shots in the match and the only one on target nestled neatly into the bottom corner by Neghli for his third goal of the season.
The Robins will have gone in at half-time wondering how they were behind but levelled almost immediately after the break, as Randell placed the ball beyond Lions keeper Max Crocombe to score his first joining the club from Plymouth Argyle in the summer.
Millwall boss Alex Neil utilised all his options from the bench to swing the momentum in his side’s favour late in the game, with Ryan Leonard, Langstaff, Danny McNamara, Joe Bryan and Thierno Ballo all introduced – and Austria international Ballo making a big impact.
Three of the replacements combined for the winner as Neghli’s clever through ball was laid off by Mihailo Ivanovic to Ballo, before the 23-year-old moved it to McNamara, whose deflected cross fell to Langstaff to apply the finish beyond Max O’Leary in the Bristol City goal.