England were held to a 3-3 draw at Wembley to end their Nations League campaign without a win.
Ilkay Gundogan and Kai Havertz had given the visitors a commanding lead but England turned the match on its head through second-half goals from Luke Shaw, Mason Mount and Harry Kane.
But a mistake from Nick Pope allowed Havertz to snatch a late equaliser for Germany.
England finish their Nations League campaign with just three points from six matches and have been relegated from the top tier of the competition after their worst run of games without a win since 1993.
In the build-up to Monday's draw, former England international Ferdinand questioned Southgate and his decision to leave Liverpool defender Trent Alexander-Arnold and AC Milan's Fikayo Tomori out of his matchday squad to face Germany.
"How is Trent not in the England squad? What's going on here?" Ferdinand said on his VIBE with FIVE podcast.
"I can't have it. I don't know how he has not taken him. He’s not even in the squad I don't understand, it's either 'I know what he is, he's brilliant, he is going to play anyway', or 'He ain't for me', what is it?
"That's the question that needs to be asked. I can't believe [it], Tomori has won Serie A, he is playing really well as an integral player in that team and can't get anywhere near the squad.
"Let alone the team, he can't get in the squad for the game. It's not like we are sitting here and going 'We've got an unbelievable amount of centre-backs to pick from by the way', give him a go and have a look, see if he can do it."
Ferdinand also questioned Southgate's decision to not call up Jadon Sancho for the games against Italy and Germany despite the Manchester United winger's impressive start to the season.
"Yeah I would have [taken Sancho]," Ferdinand added.
"Given what he has been doing at the beginning of the season. Sancho probably suits international football more than the Premier League maybe.
"Arguably you could say that, the way he plays. I don't know [why he wasn't in the squad]."
Southgate's attention will now turn to the World Cup in Qatar, which gets underway on November 20.
England take on Iran in their opening game on November 21, before facing the United States (November 25) and Wales (November 29) in their remaining group matches.
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