The changes being showcased at the Next Gen ATP Finals

The tournament in Milan, featuring the leading male players aged 21 and under, is showcasing a range of rule changes and innovations in a bid to widen the sport's appeal.

With tennis notoriously resistant to change, the ATP under president Chris Kermode has pulled off a significant feat simply by staging the event.

The draw ceremony featuring models removing clothing to reveal the different groups was spectacularly ill-judged and will not be repeated.

But some of the other experiments could be introduced to the tour and grand slams in the future.

Here, Press Association Sport takes a closer look at the changes.

Shortened sets

The most contentious of the changes is the format, with matches played over the best of five sets but with each set the first to four games. The argument in its favour is that it speeds up matches while taking away the lull that can happen at the beginning of conventional sets, and matches have certainly been more intense. But there has also been criticism that the sets have been more predictable, with a full tie-break played at 3-3 and little chance to recover a break of serve. Reaction from tennis fans has been largely negative. There may well be more experimentation with this format but do not expect to see it introduced widely any time soon.

No-advantage scoring

When a game goes to deuce, the player who wins the next point wins the game. This format is already used in doubles across the ATP Tour, where it is not popular with players. It certainly speeds up matches, but Next Gen top seed Andrey Rublev argued the scoring changes generally introduce too much of an element of luck.

No lets

If a serve hits the top of the net and lands in, it is played as a normal point. This has generally not been popular with the players, but it is something of an anachronism that shots that hit the tape within a point are played while serves are not.

Shortened warm-up

All matches start five minutes after the players enter the court. Of all the changes, this is probably the least controversial and could be introduced soon. Scrapping the warm-up entirely has also been suggested but this is a good compromise.

Shot clock

Players are allowed 25 seconds between points on the ATP Tour but currently it is up to the umpire to monitor. At the Next Gen Finals, a clock on the scoreboard counts down. The players have been universally supportive, with the clock taking away the haphazard method with which the rule is currently enforced. Rafael Nadal is a vocal critic but shot clocks were tried in qualifying and junior events at the US Open and are likely to be more widely introduced soon.

Limit on medical time-outs

Only one medical time-out is allowed per match. Another innovation that has been popular. The current system is open to abuse, with some players using medical time-outs for tactical purposes.

In-match coaching

Players are allowed to talk to their coaches during matches on the WTA Tour but not the ATP Tour or at grand slams. Unlike on the WTA Tour, the coaches at the Next Gen Finals have not come on to court but instead conversed with their player using headphones. It seems unfair that they are only allowed to do so in English, but generally this is a popular change with players while it is universally accepted that illicit communication routinely happens anyway. Critics argue players having to problem solve themselves on court is one of key tenets of tennis.

Fan movement

Instead of having to wait for changes of ends, fans - except those behind the baselines - have been allowed to come and go during points. This has received a mixed reception, and Wimbledon regulars would have a heart attack if it was introduced at the Championships. But a more relaxed approach could tie in with attracting a younger audience.