Rubio played 970 minutes. If Rubio only played 200 minutes with Garland @ +16.2, it would mean that he must have played 770 minutes without Garland @ +2.6 to reach the +5.4. So you see, doesn't have to be negative if you don't know the minutes played.
So I looked up howe many minutes he played with Garland:
LINEUPS | MIN | OFFRTG | DEFRTG | NETRTG |
.R. Rubio, .D. Garland | 512 | 112.8 | 96.6 | 16.1 |
.R. Rubio, .C. Osman | 416 | 111.1 | 98.7 | 12.5 |
.R. Rubio, .D. Windler | 108 | 105.9 | 93.8 | 12.1 |
.R. Rubio, .K. Love | 429 | 108.6 | 96.7 | 11.9 |
.R. Rubio, .L. Stevens | 125 | 113.4 | 103.1 | 10.3 |
.R. Rubio, .E. Mobley | 477 | 104.8 | 94.7 | 10.1 |
.R. Rubio, .J. Allen | 469 | 109 | 98.9 | 10.1 |
.R. Rubio, .L. Markkanen | 380 | 109.9 | 102.3 | 7.5 |
.R. Rubio, .D. Wade | 294 | 101.9 | 98.4 | 3.6 |
.R. Rubio, .I. Okoro | 341 | 102.9 | 100.1 | 2.8 |
.R. Rubio, .E. Davis | 69 | 104.2 | 105.5 | -1.4 |
.R. Rubio, .C. Sexton | 135 | 94.3 | 98.6 | -4.3 |
.R. Rubio, .D. Valentine | 85 | 91.2 | 101.6 | -10.4 |
Since Rubio played 512 minutes with Garland, you are correct, his +/- without Garland were negative ( -6.7) The off hand observation is that his early season numbers with Sexton and his garbage minutes with Valentine did it in.
Here's some random factoids from this time period: (Oct, Nov, Dec)
- Garland had better player pair numbers with K Love that he did with Rubio: +19.4 in 256 minutes,
- Garland had a worse pairing with Sexton than Rubio did: -6.3 in 187 minutes
- While Rubio had a negative +/- without Garland, Garland also had negative +/- without Rubio: -0.5 in 548 minutes. That's a contrapositive, yes?
The simplified way to look the season was that Ricky Rubio was the 6th or 7th best player on a team that was maybe 8 guys deep. Once Ricky got injured, it was really hard for Coach to keep an NBA rotation on the floor for 48 minutes a game.
The more complicated view is that the lack of a floor general off the bench hurt the team even more than the loss of Rubio's over all ability, and that was probably also true.