He admits Monday night's visit to Birmingham and the clash with Fulham at St James' Park next Saturday will be among the most important fixtures the club has played during his time on Tyneside.
Harper said: "The next two games, at Birmingham and at home to Fulham, are the biggest the club has had in a long, long time.
"We have got to get a minimum of four points from them. We cannot afford to lose either of them because they are two sides who are below us.
"We have got to go to Birmingham looking to win the game, and then we have got to beat Fulham at home."