The exclamation mark was in response to your exclamation mark after Varela.
He can't be match fit after only having 30 minutes of competitive football, that is basic football sense, and because he is not yet match fit, he won't be able to last that long if he did start the match. Your logic about starting him and then bringing him off when he tires is not a 100% guarantee because as this first half showed, the match is a close encounter and Varela would be a passenger in it.
Now Varela is ready come on and it is at the perfect time to change the game.
He can't be match fit after only having 30 minutes of competitive football, that is basic football sense, and because he is not yet match fit, he won't be able to last that long if he did start the match. Your logic about starting him and then bringing him off when he tires is not a 100% guarantee because as this first half showed, the match is a close encounter and Varela would be a passenger in it.
Now Varela is ready come on and it is at the perfect time to change the game.