The reigning MLS Cup champions conceded to Matt Hedges in injury-time at Sporting Park to be held by the Texans after taking an 81st-minute lead through Aurelien Collin.
After the match, centre-back Besler rued the late goal as the 2013 champions grabbed their first point of the new campaign.
"Any time plays happen like that, you can look at it and dissect it, and there's a number of reasons why they happen. But for us as a team, we have to lock a game down," he said.
"Right now, the first five minutes of each half and the last five minutes of each half, they're not good enough for us as a group.
"It's not one guy. It's the whole team. Whoever's out there at the beginning of the game, at the end of the game - whoever's out there, every single person on the field - we need to be tuned in, and we need to be helping out each other. And right now at the end of the game, we're not locked in like we should be."
SKC head coach Peter Vermes was also disappointed, adding: "It's unacceptable.
"It's not who we are. I'm not happy, and the guys know it. It's not who we are."
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