On his way to the team bus after a loss to the Nuggets in which Gregg Popovich would not allow him to play Tony Parker, the Spurs’ All-Star point guard, made a promise he hopes the coach will allow him to keep on Friday night. “I’m playing Friday,” Parker said without breaking stride as he focused on Friday’s game against the Kings at the AT&T Center. For a team disheartened all the more by the pre-game news that forward Boris Diaw has been ruled out of action for two to three weeks with a sprained lower back (technically, a sprained lumbar facet), Parker’s vow was music to his teammates’ ears. The Spurs leader in points scored and assists, the five-time All-Star hasn’t played since an April 4 game at Oklahoma City in which his most recent injury, a sore neck, resulted in his lowest output of the season: two points, on 1-for-6 shooting. Parker will have to convince Popovich he is completely recovered from a variety of ailments if he wants to suit up against the Sacramento Kings Friday. The Spurs coach said he would re-visit the issue with Parker after a Friday morning shootaround. “We’ll see how he feels,” Popovich said after Wednesday’s game in Denver. Opportunity knocks: With Diaw not expected to return before the playoffs begin the remainder of the regular season presents an opportunity for forward-center DeJuan Blair, a former starter and free agent-to-be who has been in and out of the lineup most of the season. “I’ve just got to be ready,” Blair said after making five-of-seven shots and scoring 12 points in 24 minutes against the Nuggets. “This is my time to show everybody what I can do, especially if (Diaw) is going to be out the first couple games of the playoffs. “I’m just trying to get better, as you saw tonight. I’m trying to score a little bit. I’m starting to get confident in my shot. The big man (Tim Duncan) gives me confidence and Pop gives me confidence. I’ve just got to keep playing in the system. “We’ve got to get better from (the Denver loss) and come back Friday.”