Christophe Fauviau, a retired military pilot, told a court in Mont-de-Marsan on Thursday that he was responsible for the death of Alexandre Lagardere and that "I'll always carry that with me".
Fauviau was accused of spiking the water bottles of his children's opponents 27 times in tournaments across France from 2000 to 2003, using the anti-anxiety drug Temesta, which can cause drowsiness.
In July 2003, Maxime Fauviau, the elder and apparently less gifted of Faviau’s two children, defeated Lagardere, who complained of fatigue after the match and slept for two hours.
While driving home, the 25-year-old school teacher crashed his car and died, with police believing he fell asleep at the wheel.
Toxicology tests showed traces of Temesta in his system, delivered by Christophe Fauviau.
Opponents of Fauviau's daughter Valentine and Maxime complained to investigators of various ills: weak knees, dizziness, nausea or fainting. Several were hospitalised.
"Not for one second did I think of hurting people. I realise now that I did," 46-year-old Faviau said.
Prosecutor Serge Mackowiack had asked for eight to 10 years imprisonment for the charge unintentionally causing death by administering toxic substances, below the 20 years maximum for offence.
In asking for the lighter sentence, Mackowiack said Fauviau had been a good soldier and said he did not seek to kill or injure the players.
"It's something that completely took me over, and I couldn't imagine that I could be responsible for the death of your son"
However, the prosecutor described Fauviau as "an adult who turned his children into objects of his own fantasies of success" and whose actions were premeditated.
"Nothing stopped you: Players collapsing on the court, the sight of stretchers, of an 11-year-old girl, a young woman who collapses against a fence. Nothing stopped you," Mackowiack said.
Fauviau asked Lagardere's parents for forgiveness.
"It's something that completely took me over, and I couldn't imagine that I could be responsible for the death of your son," he told the court last week. "I never wanted things to come out like this."
Lagardere's father, Bernard, refused to comment on the verdict, but asked that the Fauviau family remember "that in our house, there will always be someone missing."
Fauviau's 16-year-old daughter Valentine is a rising star in French tennis.
Her father is the latest and most serious example of an overbearing father in women’s tennis.
The fathers of top international players Mary Pierce and Jelena Dokic were given bans by tennis authorities for parental off-court aggression, while Richard Williams, father of sisters Serena and Venus is known for the tight control he exerted over his daughters careers and training regime.