Missing your first serve against Roger Federer in London is the beginning of the end.

Federer started slow, then rolled 6-4, 6-2 over Tomas Berdych at the Barclays ATP World Tour Finals on Sunday night, with the key dynamic of second serve returns being completely dominated by the Swiss star.

Returning first serves is almost always a defensive play, but the switch immediately flips to offence for Federer once the opponent’s first serve misses the mark.

Berdych heavily contributed to his own demise in the opening round match, only making 44 per cent (23/52) first serves, including a lowly 36 per cent (10/28) in the crucial opening set.

Federer cleverly mixed up his second serve return position, as Berdych predictably served at Federer’s body-backhand location.

There was a massive 8.2 metre (27 feet) difference from the contact point of Federer's deepest return way back behind the baseline, and the closest SABR (sneaky attack by Roger) half-volley return Federer employed twice near the end of the match.

The different second serve return tactics were simply an act of discovery for Federer, figuring out the best way to wrestle ownership of Berdych's second serve delivery on the slower indoor surface at The O2.

Federer's deepest second serve return contact point was out wide in the ad court, 3.6 metres (11.8 feet) behind the baseline, letting Berdych's high kicking delivery drop enough to attack in his backhand strike zone.

Federer only made contact with four of 18 second serve returns behind the baseline, but it was enough to create confusion in Berdych's mind as to what "first strike" tactic Federer was going to use.

Federer also employed the SABR twice, leading 6-4, 5-1, with the contact point of the first attempt a mere 70 centimetres (2.3 feet) behind the service line, and the second one 1.2 metres (3.9 feet) back.

Federer said post-match he was “in the process to find out exactly” if it is better to half-volley the SABR return, or let it rise a little higher for better timing.

“The thing is what I don’t know is how long they are going to serve,” said Federer. “You have a tendency to know which players serve it deeper into the box, and which ones serve it shorter. So, I prefer to be closer than too far, I guess, at the end.”

Berdych needed to mix more on the second serve location, hitting all 12 second serves in his opening three games of the match at Federer’s backhand wing. Federer quickly dialed in, ripping deep returns right down the middle of the court, rushing his opponent.

Federer won nine points (9/18) on his second serve for the match, but double that against Berdych’s second serve, with 18 (18/29).

Infosys ATP Insights uncovered Berdych has increased his second serve speed from 94 miles per hour (m.p.h.) to 100 m.p.h. over the past five years at the Barclays ATP World Tour Finals, but on the slower indoor surface, variety of location in the service box may be a more effective weapon for the Czech.

In the 2015 season, Federer has been ruthless once breaking serve, successfully holding 93.4 per cent of the time to consolidate the break.

Serve + 1

A key metric for Federer in holding serve, which played out heavily against Berdych, is his potent “Serve + 1” tactic, where he combines the strength of the serve immediately followed by an attacking forehand.

Federer hit 73 per cent of forehands (19/26) as the first shot after the serve on Sunday night, immediately putting Berdych on the back foot, chasing down balls out on the edge of the court.

Federer pounces on the short return, making contact with 15 of the 19 forehands inside the baseline, immediately improving his geometry to attack his tall opponent out wide.

Federer is also a master at running around returns directed at his backhand, as almost half (9/19) of the Serve+1 forehands were hit standing in the ad court.

Ultimately, Federer strategically was able to overcame “one of the worst starts I’ve had in years”, when he fell behind 0-2 with back-to-back double faults in his opening service game.

Federer’s domination with Serve+1 forehands, and swarming Berdych’s second serve from a variety of locations, can take full credit.

Overall, Federer hit six forehand winners and only two forehand unforced errors, while Berdych hit four forehand winners, but committed nine forehand unforced errors.

Federer’s masterful first strike serve and return tactics are exactly the tonic he will be seeking in his second round-robin match later this week against World No. 1 Novak Djokovic.

Craig O'Shannessy uses extensive tagging, metrics and formulas to uncover the patterns and percentages behind the game. Read more at www.braingametennis.com.