Going against the new guy.

Today I had a chance to spar with the new guy.  He is a higher belt then me and 15 years younger.  Because I am 53 when I go against the new guy (unless they are some young buck white belt who has no hespect for their Elders) they usually try not to go to hard because they don't want to break me.
The funny thing is other old guys don't take it easy but the guys in their 30's usually pull back a little.  This was a mistake on his part.  I took him down and put him in a tight side control.  I then couldn't get the bread cutter but was able to get arm triangle.  As soon as I could get across and go to mount I stepped over and really applied the pressure.  He did not tap.  Maybe because I was older and maybe because he was a higher belt or maybe it just wasn't that tight but I felt him go limp so I let up and he was able to move to half guard.

This guy was really good with the leg lock down from half guard.  I could feel a lot of pressure on my knee etc because of the way he had wrapped my leg with his leg.  I applied pressure on him and was going to work on a knee slice to clear my leg when all of the sudden he did something with my leg in his legs that was either some sort of calf slicer or ankle lock.  It felt like when you have someones back and you make the mistake of crossing your legs and they put their legs over yours and arch their backs.  I tapped.  It did not hurt bad enough to tap but I was not sure where the pressure was coming from and had no idea what he was doing so I figured best to tap.  It kind of reminded me of a kidney  stone I had over 20 years ago.  I could feel the pain and had no idea what it was.  My wife took me to the emergency room where they used some machine to break it up so it would pass.  The pain was crazy but the scary part was not knowing what was causing the pain.  Since then I have had a few kidney stones and I have just gritted it out and passed them.  I kind of felt that way with this position he had me in.  It really was not enough pain to tap when I did but I was not sure if that was all he had or if that was just the start of a move that was going to cause some serious damage if he continued on.

Now I need to know what the move was so that I can learn to defend it and also learn how effective it is.  It worked well on me.  Someone told me it might be illegal.  I am not even sure what he did as I could not see because I was on top facing forward and this was behind me.  If anyone knows that this move could possibly  be let me know.