Sterling's starting place has been the subject of debate after he produced a below-par performance in England's 2-1 win over Tunisia in Volgograd on Monday, while Rashford and Loftus-Cheek both made a positive impact from the substitutes' bench.
"I've had to analyse my game from a very self-critical point of view and be harsh on myself when things don't go well and make sure I improve in future instances".
Southgate joins Dele Alli on England's walking wounded list, with the Tottenham forward suffering from a quad complaint.
Gareth Southgate is relieved that he's the one who suffered an injury, rather than his players.
"We're going to cause them as many threats as we can using our own style of play".
While England will be expected to beat Panama on Sunday, the central Americans showed before their second-half capitulation against Belgium they are rugged and robust opponents, picking up five cautions in Sochi.
He continued: "We are lucky we have a top-class medical team around us, so it was fine". I just think what he brings, not only to the team but me personally, has been a massive, massive help.
"It is better this is me than one of the players", he added.
Gareth Southgate took England training on Thursday, despite the discomfort of a dislocated shoulder.
Southgate was initially treated by team doctor Rob Chakraverty before coming to the realisation that he had to visit a nearby hospital. In fact, he was back at the base for a team meeting and conducted proceedings with his arm in a sling. "I am just a bit gutted because I was on for my record 10k time".
"They were a bit surprised in the team meeting and were asking 'what have you been doing!?' - as always, they were probably quite amused". Here's hoping to no further injuries in the England camp.