If you are going to use the round basket type support, the best time to put these in place is at the time of planting. Putting one in after the plant is established runs the risk of damaging the roots, breaking branches, or snapping the stalk. So what is the alternative? OR if the plant is now overwhelming the basket, what is the remedy? Easy Peasie. String Trellising.
When this was first recommended to me I thought the person was a little nuts. String? Does this guy know how heavy those tomato plants get? Well, using the string would be better than finding the tomatoes on the ground so I gave it a whirl.
The grower who lives nearby uses this method exclusively to grow eight and ten foot tall tomato plants which supply the local market with some of the best tomatoes in the area. Try String trellising. You may be pleasantly surprised by the results.