Looks like it could be creeping bentgrass. You can find it along with other grassy weeds here: http://www.msuturfweeds.net/ Click on grasses . Appears to be bentgrass but a positive ID is required before taking any action. One way to do that is to send a sample to Diagnostic Services for identification for a small fee.
It is often difficult to rid of creeping bentgrass. Glyphosate, the active
ingredient in Roundup, will kill it but it is a non selective and will kill the cool season grasses as well. One option is to use it only on the bentgrass patches and then reseed the area later. Obviously it is prudent to act soon, before the invasive spreads further. There is a selective herbicide named Tenacity that is supposed to take out bentgrass without harming bluegrass and other cool season grasses but it may be available only to professional applicators.
The other option would be to involve a professional lawn care company that would ID it and handle removal for you.