Actually there's one more thing I should say if I'm going to be thorough / boring about it : the visual arm speed is really really really key.
I would have to confirm with somebody at BA but I'm not sure that the game maps delivery speed onto visual arm speed. That makes changes of pace much more difficult to pick up.
That's the key with good changes of pace. They only decieve the batsman if the arm speed looks similar to regular pace deliveries. If Bopara bowled his changes ups without disguising his arm speed he'd just go out of the park.
The popularity of the knuckle ball and holding the ball deep in the hand, is probably a big factor is making deception more effective. You don't need to adjust the arm speed just the grip. Obviously it's quite a skill to get the line and length when changing the grip but it certainly makes it easier to deceive the batter this way. Most cutters seem to be more subtle too which also means less deviation off the pitch and more subtle speed changes. The back of the hand is probably equally challenging to bowl, but potentially easier to pick.
I expect from batting perspective it requires an ability similar to picking a spinner. Although with more data and analysis available I'd imagine batters have a lot of insights into bowlers and what they are likely to bowl. I remember seeing a couple players get smacked first ball, because they like to start off with a slower ball, and the batter is expecting it. Jade Dernbach and Tom Curran, at international level, seem to have been victims of the initial success. Batters can just play them as medium pacers because they bowled so many slower balls.
Bopara seems to have made himself into a Benny Howell type variation bowler, with the quicker ball being a rare option. He looked to be bowling a lot of knuckle balls last night.
I do wonder if we're going to see more of these, certainly in franchise/domestic cricket. Bowling higher pace with variations still seems to be the preference in the top international teams. Sikandar Raza, Tim David both seem to be taking a leaf out of Sunil Narine's book with their bowling. And, I think, Narine and Raza seem to have more in common with someone like Benny Howell than other finger spinners. Although one trend I've seen over the last twelve months is finger spinners firing it in at above 70mph. Dan Mousley seems to be closer to that speed as a stock ball than Bopara or Howell.
