expression
I doubt it, but ...; I find it hard to believe, but ...; it's a long shot, but ...
Used to introduce a possibility that the speaker thinks is unlikely but still worth considering. Often followed by a conditional or a request to check something just in case.
まさかとは思うが、念のため確認しておこう。
I doubt it, but let's check just in case.
まさかとは思うが、彼が犯人かもしれない。
I find it hard to believe, but he might be the culprit.