Alonso jumped over his colleague and planted his studs on the back of Shane Long's calf.
Striker Long was forced off the field for treatment but was able to continue.
Typically these tackles look like made thoughtlessly, as a rush of blood or over dedication in direction of the ball makes the tackler lose management.
Two X-rated tackles escaped the proper punishment on Saturday as Marcos Alonso and Ben Davies ignored any ideas of security for his or her opponents.
The referee was placed only yards away from the incident and had an unobstructed view of the situation.
"If you see it again he (Dean) can clearly see it".
However, if Dean writes in his match-report that he did not see the incident in question, the FA have the option to charge Alonso for violent conduct.
These two however, appeared far more deliberate and intending to cause the opponent injury which is why the offender should be punished and the fact that can't be treated the same on review shows the importance of the referee on the day detecting and punishing them correctly.
'I think he's too close, I don't think he had the right angle, ' he told Sky Sports.
If he sees hit, he's going to give it.
If Dean saw the incident fully and decided that it did not warrant a red-card, the FA can not retrospectively ban Alonso.
Should Southampton hold on for the win, it will be enough to take them out of the relegation zone (for the time being at least) in what has been a very tough campaign for the club.
'He [Alonso] hasn't even bothered with the ball'.