Jules - See the link below for a review of your 18-140 lens. I've used this lens a few times on a D7100. From the first photo of the three players, notice the following information from the EXIF data: 140mm / 1/1250s / f/9 / ISO-400 using Shutter Priority. Rockwell's review includes the suggestion of using f/5.6 and the maximum 140mm for the best background blur this lens can achieve. You'll need to shoot using Aperture priority or manually to maintain the maximum f/5.6 aperture using this lens. But, f/5.6 isn't that wide to achieve that dreamy out of focus background. Rockwell's review rates this lens sharp wide open so you should feel confident changing to Aperture Priority. But, on a bright sunny day such as your first example, you'll need to lower your ISO and may need to use an ND filter to not overexpose.
Thank you so much for all the information. I will try this.
http://www.kenrockwell.com/nikon/18-140mm.htm

You'll also have to experiment on the resulting depth of field at f/5.6. The three players are not on the same plane where the first player might be in perfect focus but not the others at f/5.6. You can download a DoF calculator for your phone that can help you decide an f-value based on distance to the action as well preferences for the results.

All these suggestions work for your current lenses. Your 50mm has the widest aperture. I'd try that lens at f/2 to f/2.8 to balance sharpness and depth of field with a background blur. But, 50mm is pretty limited for sports / action unless you can be right next to the action. Professional lenses with a constant f/2.8 or f/4 aperture would be the next option, such as a 70-200 zoom or a 200 or 300mm prime. I'd start with the suggestions for a wide aperture first before looking for still more equipment.

Jules - See the link below for a review of your 18-140 lens. I've used this lens a few times on a D7100. From the first photo of the three players, notice the following information from the EXIF data: 140mm / 1/1250s / f/9 / ISO-400 using Shutter Priority. Rockwell's review includes the suggestion of using f/5.6 and the maximum 140mm for the best background blur this lens can achieve. You'll need to shoot using Aperture priority or manually to maintain the maximum f/5.6 aperture using this lens. But, f/5.6 isn't that wide to achieve that dreamy out of focus background. Rockwell's review rates this lens sharp wide open so you should feel confident changing to Aperture Priority. But, on a bright sunny day such as your first example, you'll need to lower your ISO and may need to use an ND filter to not overexpose.

I took your wonderful advice. Here are a few from your tips I took yesterday. Thanks again.
http://www.kenrockwell.com/nikon/18-140mm.htm

You'll also have to experiment on the resulting depth of field at f/5.6. The three players are not on the same plane where the first player might be in perfect focus but not the others at f/5.6. You can download a DoF calculator for your phone that can help you decide an f-value based on distance to the action as well preferences for the results.

All these suggestions work for your current lenses. Your 50mm has the widest aperture. I'd try that lens at f/2 to f/2.8 to balance sharpness and depth of field with a background blur. But, 50mm is pretty limited for sports / action unless you can be right next to the action. Professional lenses with a constant f/2.8 or f/4 aperture would be the next option, such as a 70-200 zoom or a 200 or 300mm prime. I'd start with the suggestions for a wide aperture first before looking for still more equipment.