really depends how well you know the game, the teams and the venue.
If you are referring to those sports day in the sunny outdoor field type of event, a 18-2xx lens will do the job. For those held at indoor venues, i recommend at least f/2.8 lens and do take note of the iso.
Unless you are the type to machine gun, for indoors i recommend Raw.
Any tele lens will do, and I think your current lens (18-105) is good enough..
Or probably you could consider renting the mighty 70-200/2.8
No point buying those expensive tele lens if you never use it again after 1 event