Peter Houston is tired of seeing his player make mistakes that cost them games. He wants them to eliminate the mistakes which have contributed to recent poor results. United were 2-1 losers at Tynecastle on Sunday after Brian McLean and Gavin Gunning fail to clear the ball allowing Ryan Stevenson to score before the Hearts midfielder scored his second from the penalty spot. A goal from Keith Watson was not enough to spark a second as United dropped below the Edinburgh side in the table. That result came a week after seeing a seven and a half minute three-goal lead slip against Inverness with a last minute penalty required to salvage a point. No wonder Houston has called for United to tighten up and add to their two home wins this season when they meet St Johnstone on Wednesday. Houston said: "St Johnstone's a tough match, but we have to start putting a run together with regards to our home form. Our away form has been good. We played well (at Hearts) and lost the match, but we have to make sure we start a wee run at home. We have to clear our heads of our result and try to get a result against St Johnstone on Wednesday. We have to really, really stop giving soft goals away. We have to make sure we cut out the errors that we're making. We can play as good football as any team in the league in my opinion, out with Celtic." Houston has lost defender Sean Dillon to a thigh injury and he is unlikely to return before the winter break. Refering back to the error that opened the scoring for Hearts, Houston was asked if he would consider playing captain Jon Daly to centre back Stiker Dalyplayed in defence earlier in the season, but alongside Johnny Russell is part of a potent strike-force. Houston said: "No. He's near the top of the scoring charts already with eight goals, having played a few times (in defence). Brian McLean's been playing excellent the last few weeks and I don't blame Brian for losing the match. He made an individual error, he put his hand up, but it cost us. Wee individual errors are costing us."