Blackpool have signed Derby striker Kwame Thomas on a six-month loan.
Crawley have signed former Birmingham goalkeeper Callum Preston on a one-year contract.
Boro are in the market for new recruits, and forward-thinking talent figures prominently on their summer shopping list.
It had been suggested that they would look at landing Napoli striker Vargas on loan, with the Chile international having struggled to settle in Italy and been returned to South America on a short-term deal at Gremio.
Vitor was also said to be a target for Mowbray, with the Portuguese midfielder currently contracted to Pacos de Ferreira.
Boro are, however, tracking a number of targets and may be about to turn their attention elsewhere in the pursuit of fresh faces.
Mowbray told the Gazette: "I think they are probably players that have been very much on the radar but have drifted a little bit.
"They are players that we have looked at in-depth, players that we've talked about and had certain discussions with.
"But there are still other players that we are looking at."