I didn't watch the match live, but for those interested here's a video of the match. The illegal move occurred just after the 4:25:35 mark.
Here's the original position (before the 61 has been played and before the 53 was rolled):
  White is Player 1
score: 16 pip: 79  17 point match Crawford  pip: 180 score: 15
Blue is Player 2  
XGID=CbEDbaaBaaabbbA:0:0:1:61:16:15:1:17:10 
Blue to play 61 
1.  Rollout^{1}  19/13 8/7  eq: +1.029 
 Player: Opponent:  75.54% (G:25.89% B:2.94%) 24.46% (G:15.04% B:1.06%)  Conf.: ± 0.024 (+1.004...+1.053)  [100.0%] Duration: 2 minutes 31 seconds 

2.  Rollout^{1}  20/14 8/7  eq: +0.941 (0.088) 
 Player: Opponent:  73.31% (G:23.72% B:2.67%) 26.69% (G:17.22% B:2.11%)  Conf.: ± 0.025 (+0.915...+0.966)  [0.0%] Duration: 2 minutes 29 seconds 

3.  Rollout^{1}  18/12 8/7  eq: +0.925 (0.104) 
 Player: Opponent:  73.02% (G:23.20% B:1.59%) 26.98% (G:17.42% B:1.57%)  Conf.: ± 0.027 (+0.898...+0.951)  [0.0%] Duration: 2 minutes 21 seconds 

4.  Rollout^{1}  12/6 8/7  eq: +0.890 (0.138) 
 Player: Opponent:  70.88% (G:23.63% B:1.98%) 29.12% (G:18.24% B:1.83%)  Conf.: ± 0.027 (+0.863...+0.917)  [0.0%] Duration: 2 minutes 14 seconds 

5.  3ply  19/13 7/6  eq: +0.726 (0.303) 
 Player: Opponent:  67.88% (G:18.41% B:0.80%) 32.12% (G:18.58% B:0.59%)  


^{1} 324 Games rolled with Variance Reduction. Dice Seed: 28077514 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.prerelease, MET: Kazaross XG2
Knowing his opponent's next roll (a 53) Ed could consider 20/14 8/7, but an XG rollout still likes his actual play (19/13 8/7). According to the rollout, Ed is +0.901 after 19/13 8/7, but only +0.861 after 20/14 8/7. Both moves give him 28 shots at the 8point blot. After 20/14 8/7 only 53, 52, 32, and 21 miss. After 19/13 8/7 only 63, 62, 61, and 21 miss. In addition 19/13 8/7 keeps the 20 point.
After 19/13 8/7:
  White is Player 2
score: 15 pip: 173  17 point match Crawford  pip: 79 score: 16
Blue is Player 1  
XGID=CbEDbaBaabbbbA:0:0:1:53:16:15:1:17:10 
Blue to play 53 
1.  Rollout^{1}  Bar/17  eq: 0.901 
 Player: Opponent:  27.58% (G:17.99% B:2.25%) 72.42% (G:22.62% B:2.26%)  Conf.: ± 0.011 (0.912...0.890) Duration: 9 minutes 30 seconds 


^{1} 1296 Games rolled with Variance Reduction. Dice Seed: 28077514 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.prerelease, MET: Kazaross XG2
After 20/14 8/7:
  White is Player 2
score: 15 pip: 173  17 point match Crawford  pip: 79 score: 16
Blue is Player 1  
XGID=CbEDaaaBaabbbbA:0:0:1:53:16:15:1:17:10 
Blue to play 53 
1.  Rollout^{1}  Bar/17  eq: 0.861 
 Player: Opponent:  29.62% (G:19.71% B:2.18%) 70.38% (G:22.66% B:1.82%)  Conf.: ± 0.013 (0.874...0.848)  [99.9%] Duration: 9 minutes 24 seconds 

2.  Rollout^{1}  Bar/22 10/5*  eq: 0.894 (0.033) 
 Player: Opponent:  29.56% (G:20.64% B:3.21%) 70.44% (G:24.26% B:2.69%)  Conf.: ± 0.015 (0.909...0.879)  [0.1%] Duration: 10 minutes 12 seconds 


^{1} 1296 Games rolled with Variance Reduction. Dice Seed: 28077514 Moves: 3ply, cube decisions: XG Roller

eXtreme Gammon Version: 2.19.211.prerelease, MET: Kazaross XG2