Ki Sung-Yueng helped Celtic keep the pressure on Scottish Premier League leaders Rangers with a crucial goal in their 2-0 win over St. Johnstone at McDiarmid Park. Neil Lennon\'s side kicked off seven points behind Rangers after their Glasgow rivals\' late win over Inverness Caledonian Thistle yesterday. But two goals in four minutes from Gary Hooper and Korea Republic midfielder Ki midway through the second half ensured that gap was reduced to four points. Hooper broke St. Johnstone\'s stubborn resistance on the hour and Ki sealed the points moments later with his first goal in nine matches. The only downside for Lennon was the loss of Swedish defender Daniel Majstorovic, who had to go off in the first half with a suspected fractured cheekbone after a clash of heads with Saints midfielder David Robertson. The visitors first threatened when Georgios Samaras drew a fine save from Peter Enckelman with a long-range strike. Then Saints defender David McCracken was relieved to see his attempted header clear from Cha Du-Ri\'s cross loop over his own goal for a corner. Then Celtic striker Hooper missed a great chance to open the scoring. He latched onto a pass by Cha inside the penalty area and dummied Enckelman but the goalkeeper somehow got his hand to the shot to push it past the post. St, Johnstone started the second half strongly and within a minute captain Dave Mackay cut inside his Celtic counterpart Scott Brown and drove in a left-footed shot which Fraser Forster saved down low at his left-hand post. But Enckelman had to make another great save from Hooper in the 57th minute and Celtic\'s increased pressure was rewarded in the 60th minute. Saints failed to clear a Charlie Mulgrew corner and Hooper squeezed his shot home from close-range. And Celtic doubled their lead four minutes later with a breakaway Ki goal after a flowing move involving Cha and Samaras ended with the South Korean slamming in from close range.