SID Nelson has joined League Two side Swindon Town on loan until January.
The 22-year-old agreed a one-year contract at Millwall in June but will spend the first half of the season at the County Ground.
Nelson's first-team opportunities looked limited after the signing of Murray Wallace from Scunthorpe United and Byron Webster returned from a long-term knee injury.
Swindon boss Phil Brown was in the stands at Welling United on Monday night as Nelson featured for a Millwall XI in a 1-0 victory at Park View Road.
Nelson spent the first half of last season on loan at Yeovil Town before moving to Chesterfield in January and despite some impressive performances, he was unable to save the Spireites from relegation.
The Defender is yet to play in pre-season for the Lions first-term and hasn't appeared for Millwall since April 2017.
Image: Millwall FC