HOUSTON – On Tuesday, Timberwolves backup center Chris Johnson blocked six shots - five of them in the second quarter alone — against an undermanned, undersized San Antonio Spurs team.

On Wednesday, he and fellow backup center Greg Stiemsma discovered, unsuccessfully, what it's like to try and impede 7-2 Indiana center Roy Hibbert while starter Nikola Pekovic nursed strained abdominal muscles back home in Minneapolis.

"Totally different," Wolves coach Rick Adelman said.

The Wolves beat the Spurs by 24 points on a night when Tim Duncan stayed home in San Antonio while Johnson and Stiemsma swatted shots and altered others all night long.

They lost by 17 the next night in Indianapolis when Hibbert exerted his sheer physical presence and scored 17 of his season-high 27 points by halftime. Nine of his 12 rebounds came on the offensive backboards, and he blocked four shots, too.

"Some nights it goes your way in the NBA," Johnson said after he played just nine-plus minutes against the Pacers one night after he played 22 against Spurs. "Some nights it doesn't."

Johnson signed with the Wolves out of the D League in January about the same time the team brought Mickael Gelabale over from Europe to supplement an injury-ravaged roster that was shorthanded then and nearly two months later remains shorthanded now.

The Wolves released veteran Lou Amundson in early February so they could sign both players for the rest of the season, and probably beyond.

If he's not with the Wolves, then he'll probably still will be somewhere in the NBA.

"I think both can play in the league," Adelman said. "Chris has to get stronger, and you have to find a spot for him. But Gelly, certainly, has the ability the play in this league."

Johnson is 6-11, 27 years old and listed at 210 pounds.

That's right, 210 pounds.

That spot to which Adelman referred has been elusive. When Pekovic is healthy, Adelman often finds little or no playing time for Johnson behind Pekovic and Stiemsma.

When Pekovic is injured, as he is again now, Adelman picks and chooses the right times and matchups for Johnson, certainly less often than some Wolves fans infatuated with his long arms and lively body would like.

He's the one Wolves big man springy enough to get to the rim to put the oop into Ricky Rubio's alley.

"He's young," Adelman said of a former LSU center who played briefly with Portland and New Orleans in between stops in the D League.

"He has to learn how to play. He has the quickness and jumping ability, but he hasn't learned how to use that yet. He just gets a little overmatched."

On Tuesday, he thrived.

"I really didn't even know it until after the game," Johnson said, referring to those five blocks in one quarter. "I just remember two of them. It just felt normal to me, really."

On Wednesday, he fought to survive against Hibbert and thicker, stronger Ian Mahinmi and Tyler Hansbrough. He played 9½ minutes, made all three shots he attempted and collective five fouls in that short time as well.

"I agree, I just have to get stronger," said Johnson, whose team ends a quick two-game trip tonight in Houston. "That's the only thing that's probably holding me back right.

''I've been skinny my whole life. I faced bigger guys. That's nothing new to me. You have to work with what you have. You can't gain strength overnight. I work on it, just lifting [weights]. I can eat all day. It's just not sticking anywhere.

"I feel like I belong here. I just have to keep working with what I have, and that's quickness and outsmarting someone with what I do have."