Pair #1: Tre Jones and Bryn Forbes
Theoretically, having Tre Jones and Bryn Forbes on the court together could make some interesting things happen on offense. While Jones can wreak havoc in the pick and roll and snake past defenders with his shiftiness, Forbes could work his magic off the ball and find openings behind the three-point line. In this way, they kind of balance each other out on that end.
Personally, though, I have serious concerns about their defensive potential. Never mind the fact that Jones was the ACC Defensive Player of the Year in college. With Jones and Forbes being listed at 6'1" and 6'2", respectively, they would immediately be one of the smallest backcourt duos in the league.
While Jones could get away with being that size in college, in the NBA, that will be a bit of a hindrance on defense no matter how one looks at it. His 6'4" wingspan and only slightly above-average athleticism only make matters worse and I anticipate him having a good amount of trouble with bigger, stronger guards.
Forbes is about the same size and, although he may have picked up a thing or two on defense in Milwaukee, I doubt that it's enough to offset his flaws. While he isn't exactly a lazy defender or incapable of making good reads, he will have similar limitations to Jones and has never had a knack for good positioning or instincts to compensate.
Ultimately, if these two were to play together, it would require the Spurs' best frontcourt defenders' presence on the floor. A lineup of Jones, Forbes, Devin Vassell, Thaddeus Young, and Jakob Poeltl could work, but I doubt Poeltl sees much playing time when at least a couple of other starters aren't on the floor. Even then, though, scoring could be a big concern for that group.