In front of that kind of opponent, I think my superficial, sharp-looking technique would have been seen through and I would have lost.
Literal
That-kind [gen-の] opponent [gen-の] front [at-では], my show-on-surface [only-だけ] [gen-の] clever technique [topic-は], see-through-[passive-かれた] time [at-に] was-losing [quot-と] think.
見せ掛けだけ 'just for show / only on the surface' uses 見せ掛け (the noun form of 見せ掛ける 'to pretend / put on a show of') + だけ 'only.' 怜悧 (れいり) '(intellectually) sharp / clever' is a literary adjective. 見抜く 'to see through / discern' is a compound verb (見る + 抜く). 見抜かれた時には負けていた 'when seen through, I would have (already) lost' uses the past continuous 負けていた, a counterfactual-sounding 'I would have (been) losing.'