as likely as not|
very probablyAs likely as not she's forgotten all about it.The illness was caused, most likely, by a virus.
Usage note: likelyIn standard British English the adverb likely must be used with a word such as most, more or very: We will most likely see him later. In informal North American English likely is often used on its own: We will likely see him later. ◇ He said that he would likely run for President.