There isn't any carryover for this statistic to training because of the rest intervals in tennis, as well as the difference in movement patterns. Running forward in a straight line at a constant speed for one single period of time will not condition you to move laterally as quickly as possible from a stop for a 2 hour match that has ~10+ seconds of rest between each point.
Well, running in a straight line is going to make you faster moving laterally and faster sprinting forwards and backwards, but it does so indirectly. Essentially, we all need a BASE LAYER of training, which prepares the body to do the training that will make you faster. If you had students to coach, you wouldn't simply start them off with sprinting drills, fast lunges, etc. You'd do what McEnroe does, have them run 5 miles for base conditioning, and follow up after a few weeks with the speed stuff. I don't want to go into the metabolic systems, pathways, and trainining zones here, but there are plenty of web sites that explains this sort of thing. I remember in the 1960's I was in Tampa at a big tournament and a Mexican player was there training on his off day. My buddy and I were hitting on an outside court watching him train. I can't remember the guy's name but this was back in the days when the Mexicans had 4 or 5 very good players and he was one of them. Anyway, we stopped our play and in pidgeon Spanglish we chatted about his training. He said he was going for a three mile run, so we decided to run together. At that time, I could run high 15's fairly easily for 5K, so I didn't think this guy would be much to handle.
We ran easy for about a mile and then we kicked up the pace. Soon we were running around 5:15 or so and he was barely breaking a sweat. My buddy had faded back about 400 meters with about half a mile to go. This Mexican guy just kicked it up a gear right at the end, and I was dropped! I held on but he beat me easily by about 15 seconds or so. Now, that was back in the day when distance running wasn't that popular with the playing pros, but today, lots of pros do 3-10 mile runs.
I wish I could tell everyone not to bother with distance running, but I'm a big believer in the value of that conditioning. If you are older, do less of it, and throw in some biking which is easier on the body.
Just my humble opinion and I'm sure I'm wrong as usual.
-Robert