Collocations for implausible - adj.

be, seem, sound
consider sth, deem sth
These results might be considered implausible.

extremely, fairly, very, etc.
highly
totally, utterly, wholly, wildly
This idea is totally implausible.

increasingly
He gave a series of increasingly implausible excuses.

not entirely
inherently
biologically, psychologically, scientifically, etc.

Implausible is used with these nouns:
explanation