The "choke factor" in tennis betting

You probably have seen this somewhere. These fans' rants online or newspapers' articles where reporters and writers accuse a player. Most of such things are related to a player "chocking" the game or the important moment of it. 

Such "chokes" usually take place during the key moments, like the serving for a set or match point. These situations impose a great amount of stress even on elite veterans, which puts players' mental strength and self-control on a test.

One research has shown that players tend to mess up more set or match servers than any other. This happens due to the aforementioned stress and great responsibility. Besides being an important moment, such servers are more memorable and valuable for the fans, they receive more attention from the media, etc. All of this combined results in players being a little shaky when it comes to these serves.

Based on this information, you can tell right away that players may struggle with self-confidence when it comes to the very last moment. 

The very next thing we would like to look at is the actual ranking and whether it affects the winning chances of the underdog. For example purposes, we would like to use the data from 2014, which includes all the players that received a 5.00 (4/1) odds and were wagered on with a £100 stake.

What exactly is a "choke factor"?