"Foreign signings are a fact of life because this is a global league," he said. "English lads are no longer just fighting with lads from Ireland or Scotland or Wales like it was historically.
"But they've got to make sure they embrace that challenge."
Boro's injury problems have forced Southgate to regularly dip into the club's academy for his matchday squads and he will continue to give local talent a chance to shine.
"At Boro, we've brought through a vast number of players from the academy into the first team," he said.
"Whether ours are better than anybody else's I don't know, but what they've had is an opportunity.
"Without them, we'd have been very short. It also give our club a bit of a heart beat to have players form the town.
"Boro are the sort of club that has pride in its local talent.
"But the challenge facing these players is to fight off the foreign invasion and make sure they are vindicated.
"They commit themselves to that challenge."