Best tennis fitness training during winter season?

[New Daddy]

I live in a region where the winter is harsh and indoor courts are expensive.
What would be the best tennis fitness training for someone like me during the winter season?

[thursdayisgod]

do ripptoes, it's a lifting program designed for athletes, google it.

[Solat]

ripptoes looks like it's for muscle building which is not that beneficial to tennis

i'd suggest plenty of agility runs and short distance fartlek training (google it). Also plenty of core stability and balance work