That makes it now just one defeat in the last 12 games for Martin O’Neill’s side as the build-up to next summer’s finals in France continues.
The Netherlands are the next visitors to Dublin for a friendly on Friday, May 27th.
Ireland manager O’Neill named ten changes from Friday night with striker Long the only starter from that 1-0 win over Switzerland.
The Southampton man was partnered in attack by McClean in a 4-3-1-2 formation with Wes Hoolahan in a free role behind them.
Slovakia, captained by Liverpool’s Martin Škrtel, included in their starting XI fellow defender Kornel Saláta and veteran striker Róbert Vittek who both scored in a 5-1 Europa League win for Slovan Bratislava over SSE Airtricity League side UCD on a previous visit to Dublin last summer.
In a lively start to the game, with eventual man-of-the-match Hoolahan prevalent, Ireland’s front two carved the first opening from a 12th minute counterattack.
Long burst clear from the back following a Slovak corner. He fed McClean who cut in from the right to drill a low, left-foot shot which Matúš Kozáčik got down well to stop.
A minute later, though, Slovakia clinically punished Ireland in a swift breakaway of their own.
Erik Sabo’s foot looked very high as he nicked the ball over the head of Paul McShane on the halfway line to race away down the Slovak’s right flank. The midfielder’s precise pullback was powered to the net by Miroslav Stoch with a crisp right-foot finish.
As was the case with Kevin Doyle on Friday, an injury befell Ireland early on as goalkeeper Rob Elliot hurt his right knee in attempting to make the save for the goal and left the field on a stretcher to be replaced by Darren Randolph.
Slovakia’s lead was short-lived, however, as Ireland were level on 21 minutes.
Eunan O’Kane put Long in on goal and he was adjudged to have been taken down by Kozáčik. Long picked himself up to send the Slovak keeper the wrong way from an emphatic penalty, his 15th goal for Ireland.
If the award of that spot kick by Norwegian referee Ola Ober Nielsen was somewhat harsh, there was no doubting a second penalty given to Ireland just three minutes later.
Again it was Long’s marauding running causing the visitors’ defence problems as Škrtel took down the Tipperary man as he surged into the Slovakia box.
This time, McClean took the spot kick. Kozáčik dived correctly to his left but couldn't prevent the West Brom winger’s drive finding the corner of the net for what was his fifth goal for his country.
Ireland were close to extending their lead from a 33rd minute corner, but skipper John O’Shea’s header was blocked by a defender before being frantically cleared.
In an action-packed first half, an own goal then gifted Slovakia an equaliser right on 45 minutes.
Stanislav Šesták put Peter Pekarík away on the right and his cross from the end line ricocheted into the net at the near post off Vittek.
In a less frenetic second half, it was the hour mark before the game produced a shot on target as Stoch galloped forward to shoot straight at Randolph.
Ireland responded with half-time substitute Robbie Brady having a free kick deflected over the bar two minutes later. Hoolahan’s shot was then blocked as Slovakia failed to properly clear Brady’s resulting corner.
The Slovaks had more work to do minutes after that when scrambling clear following Brady’s header after Cyrus Christie did well to get forward on the right to cross.
RepublicofIreland: Elliot (Randolph 16); Christie, O’Shea (Pearce h-t), McShane, Ward (Hayes 79); O’Kane (Pilkington 66), Whelan, McCarthy; Hoolahan (McGeady 73); McClean, Long (Brady h-t).
Slovakia: Kozáčik; Pekarík, Škrtel, Saláta, Švento (Tesák 88); Greguš (Hrošovský 74), Sabo (Duda 65); Šesták (Weiss 66), Hamšík, Stoch (Mak 65); Vittek (Nemec 65).
Referee: Ola Ober Nielsen (Norway).