Marcus Smart was on his game Monday night, tallying a season-high 23 points on 61.5 percent shooting (8-for-13). Which, it turns out, is bad news for the Boston Celtics. The Celtics lost for just the fourth time this season, falling to the Detroit Pistons 118-108 at TD Garden despite Smart’s best efforts. But this isn’t the first time they’ve failed while Smart has succeeded. Check out this crazy stat from ESPN’s Chris Forsberg That’s right: The Celtics have won every game in which Smart has been atrocious offensively. (The league average shooting percentage was 45.6 entering Tuesday). And the young guard has shot well (by his standards) in all four of Boston’s losses to date. How the heck does that make sense? Shouldn’t the C’s perform better when one of their most important role players is hitting his shots? Such is the conundrum presented by Smart, a ferocious defender and historically awful shooter who can have a massive impact on games despite hoisting a steady stream of bricks.