The cliche has been used many times to describe Isaiah Thomas on offense -- he is the “head of the snake” for the Sacramento Kings.

Thomas said after Monday’s practice he has to be the same thing on defense. Charlotte point guard Kemba Walker torched the Kings for 30 points last Saturday. It doesn’t get any easier for Thomas Tuesday night when the Kings host the Portland Trail Blazers.

Portland’s point guard, Damian Lillard, could earn his first All-Star Game appearance this season and is bigger and maybe even quicker than Walker.

Thomas said he hasn’t been aggressive enough on defense lately.

“Lately I’ve been watching film and I’m not putting enough pressure on the ball so the guard is not able to drive on me all the time but make passes when he wants to and he’s comfortable out there,” Thomas said. “So I’ve got to make it more for a guard to be uncomfortable. It starts with me. If I pick up, not fullcourt, but if I pick up the pressure, guys will say OK, let’s follow his lead and I’m going to try and do that tomorrow night.”

Thomas is far from the only culprit for the defensive struggles. The Kings haven’t contained the ball on the perimeter most of the season. Defensive rotations have been slow or nonexistent from the bigs or other wings.

But Thomas looking to do more to disrupt opposing offenses is the right place to start. Too many opposing point guards have had their way against the Kings as scorers and distributors.

“Coach (Michael Malone) always says don’t rely on your help but trust your help,” Thomas said. “So don’t get beat before you get beat is basically what he’s saying. As an individual we’ve got to lock in. We’ve got to lock in and worry about our guy not scoring. And at the same time the help defense can’t worry too much about their guy scoring because I think that’s the big thing with us.”

*The Kings waived center Hamady Ndiaye Monday. The Kings’ roster is down to 13, leaving two spots open for free agents or trades.

*Carl Landry (torn left hip flexor) is able to participate in drills in practice, but is not practicing with the team yet. He’s been out since injuring his hip during training camp in October.