Minato's Senjutsu Mastery

Kakashi: "If I recall correctly...
...Senjutsu isn't your forte, master..."

Minato: "That's an understatement. It takes me too long to build up the chakra, plus I can't maintain it long.
I haven't used it much in real combat, either." 

Takl, Minato: ............
Kakashi: ....sensei, if I remember correctly, you were ..
er... sen jutsu isn't so much.... 
Minato:...to be honest, im poor at senjutsu, you know. 
(with Sen jutsu) i take too much time to knead up chakra and I cant keep it up for a long time to boot. 
I havent used it (=senjutsu) much in actual fighting.
Minato: furthermore, presently I'm not in a condition to perform(/put up) (hand) seals that I don't even think I can fight properly.