When Romelu Lukaku was on loan at Everton last season, an agreement between the sides prevented him from playing against Chelsea.
No such anti-competitiveness provision exists in Russian football, with Diniyar Bilyaleydinov allowed to play for his rival club against his owners.
The former Toffee had fallen out of favour at Spartak Moscow, and was sent out on loan to newly promoted side Torpedo Moscow on deadline day.
He made his debut for Torpedo in the match against Spartak on Sunday in the Russian Premier League, and was lively throughout.
Bilyaletdinov created six goalscoring opportunities in the hour he played, but it failed to yield any result.
Torpedo were out-gunned 3-1, with young Dutchman Quincy Promes bagging two for a Spartak Moscow side which contained former Arsenal loanee Kim Kallstrom.
Most impressive statistically, was Bilyaletdinov creating the six chances from only 29 touches of the ball, taken off early owing to a lack of fitness.
It appears though he has found a side willing to give him a run of games and try to get his career back on track which has stalled since returning to Russia, and the opening flashes on his debut bode well.