Aberdeen and St Mirren both have something to prove tonight. Aberdeen welcome St Mirren tonight on league business but they could be without Zander Diamond for the game. The Dons defender came off during Saturday's 2-0 defeat by St Johnstone with a hip injury and is struggling to be fit. Aberdeen boss Craig Brown will consider giving a start to Fraser Fyvie who came off the bench against Saints after recovering from after a cruciate ligament injury. Assistant boss Archie Knox admits the imminent exodus of players from Pittodrie contributed to Saturday's home defeat to St Johnstone. Derek Young, David McNamee and Mark Howard will leave the club at the end of the season as loanees Steven Smith, Nikola Vujadinovic and Nick Blackman also leave to return to their parent clubs. Zander Diamond's contract is up at the end of the season and is rumoured to be signed by Hearts. Aberdeen manager Craig Brown is also expecting Sone Aluko to return to English football in the summer while Chris Maguire and Jamie Langfield have to make decisions on the contracts that have been offered. The Dons put up a disappointing display in the 2-0 defeat by Saints. Knox was asked if the uncertainty affected the players. He said: "I think it must do. You are always going on to players that every time they take to the football field they have to perform. Knowing full well that a few of them might be out next season, it is difficult for them to motivate themselves. That's no excuse on their part but invariably that's what happens, especially in the position we are in. We can note the injuries and certainly we have an injury list which is crippling but you are always looking for the right application and St Johnstone were better at that than us.'' St Mirren go into the game with Jim Goodwin rated as "very doubtful". Goodwin limped off with a calf strain 40 minutes into the Paisley side's 1-0 defeat by Inverness on Saturday. Hugh Murray (knee) is out for the season but Jure Travner is available following suspension. Manager Danny Lennon hopes that facing their fears in a group discussion will allow his players to brush off the tension and secure their SPL status. Saints looked safe when they followed up a win over relegations rivals Hamilton last month with a convincing win over Aberdeen to move 12 points away from the bottom. However, Hamilton's revival has seen them reduce the deficit to three points with two game left. Lennon felt his team were frozen by fear when they lost 1-0 in Saturday's game in Inverness. So he encouraged them to talk through their anxiety in a bid to ease the pressure ahead of their trip to face Aberdeen tonight. Only three first-team players are contracted to the club for next season, with Lennon awaiting confirmation of their league status before he can shape his squad. But he has told them he will take responsibility for their final two games against the Dons and St Johnstone. Lennon said: "We had a very good meeting yesterday with the players. We are all disappointed with the last two results: the coaches, the players, the directors and fans, none more so than myself. We were on the back of a good run of performances but now we are at the business end of the season, so many players are out of contract soon and worried about their futures." Saints will stay in the SPL if they record a better result than Hamilton against St Johnstone, and a win in one of their remaining two games would almost certainly seal their survival given their eight-goal advantage over Accies.