I thought I’d have a look at which PL outfield players are yet to play this season (excluding those who are injured or recently signed):
Arsenal: Kiwior, Jorginho, Nketiah (Nelson has played two minutes)
Villa: Buendia, Carlos, Hause
Bournemouth: Aarons, Anthony, Hill
Brentford: Toney, Yarmolyuk (Mee has played one minute)
Brighton: Lamptey, Moder, Igor (Sarmiento has played eight minutes)
Chelsea: Lukaku, Chilwell, Sterling, Chalobah, Broja, Casadei, Chukwuemeka, Datro Fofana
Palace: Franca, Ward, Holding, Clyne (Schlupp has played eight minutes)
Everton: Maupay (Holgate has played five minutes)
Fulham: Mbabu, Vinicius, Castagne (Reed has played five minutes, and Stansfield one minute)
Ipswich: Burgess
Leicester: Thomas, Cannon, Nelson, Pereira, Choudhury (McAteer has played nine minutes)
Liverpool: Phillips, Doak, Bajcetic, Gomez (Elliott has played seven minutes, and Endo one minute)
Man City: Cancelo, Kabore, Walker (Ake has played one minute)
Man Utd: Hannibal, Eriksen (Antony has played one minute, and Sancho seven minutes)
Newcastle: Fraser, Hayden, Lewis, Targett, Willock (Almiron has played one minute)
Forest: Dennis, Omobamidele
Spurs: Reguilon, Lo Celso, Solomon, Davies, Dragusin (Solomon apparently having a medical with Leeds)
West Ham: Zouma, Cornet, Aguerd (Cresswell has played one minute, and Ings five minutes)
Wolves: Semedo, Silva, Traore, Guedes, S Bueno, Cundle
Obviously not every player above will be available to move (whether on loan or permanently). But I would suggest that a sizeable number could be available, whether to move abroad, or to another PL team, or down to the Championship.
There are a few names there who I would be interested in for Saints. But the out-of-favour PL player who I'm most interested in (most likely on loan) isn't listed above, because he played 16 minutes for West Ham on the opening day.