I don't know exactly what a 'Blue Agave' is, but I would probably remove what looks like pups (the thicker rhizomatous wandering 'roots') -- unless you want pups, then trim off the bottom inch or so of the rootball. Pot up in same pot. Keep on the dry side for a week or so, then resume regular watering.

These require harsh treatment to remove excess and dead roots. I use a gardening fork (a small one used by one hand) to lever apart the roots in the root ball. I tease away the roots by hand after they have been loosened and this removes the dead roots from inside the root ball. Even so, you are left with too many roots and I usually simply cut the longer ones back. Break off the thick roots with pups forming on the end. I would normally pot into a larger pot as the roots won't fit easily into the existing pot and there is not much room for potting mix as well, and difficult to get the potting mix in amongst the roots.

These plants are very robust. You can leave for a week before repotting to let the cut roots heal but personally, I repot straight away and don't water for a couple of weeks to let the roots heal.

If you don't remove all the excess roots and simply put into a larger pot, the roots will stay within the root ball and not venture into the new potting mix, so you don't gain anything by repotting.

Don't be afraid to be brutal with your removal of the roots. I remember a demonstration of separating orchid bulbs where they used two garden forks (full size) to lever apart the clump. No tender treatment at all.

I'm with sg, but perhaps even more so - take your pruning saw and remove 1/3 to 1/2 of that root ball - just cut it off and set the plant aside for a day, then repot.

Great. Thank you! Very helpful!

Here is what I did today, biting my nails that I didn't go over board with cutting the root ball to much. If so I got plenty of pups to work with.

Looks good.

It may take a while to generate new roots but it should be okay. I had my A. parryi truncata sitting outside its pot all winter. I potted it up a couple of weeks ago in a small pot of potting mix and sand on top. Roots are probably half an inch now.

Here it was last year sitting in this bare iron basket all summer and all winter (indoors) with two offsets. The bottom did have some rot so I had to trim it away to healthy tissue and some of the lower leaves as well.

It was also a breeding ground for ants so I drowned most of them in this small bucket.

I will take some photos when I remember of it in its small clay pot now.

Here are some other agaves just plunked into trays of perlite. I just need to find the time to pot them up. This was in Feb.

The problem with agaves is they can get huge and they do have some pretty wicked teeth. I had to downsize this one because it was heavy and hard to move without poking one's eye out.

I finally took some photos of the agave parryi I stuck in a pot a few weeks ago (after sitting out of one for nearly a year).

Yay. Happy plant!