Schalke missed a chance to grab the lead in the German Bundesliga as they could shared the points at Hamburg.
Ruud van Nistelrooy opened the scoring for the visitors after 40 minutes. Kevin Kuranyi levelled the game in the 62nd minute and Ivan Rakitic converted a penalty six minutes later for a 2-1 Schalke lead. But Jonathan Pitroipa gave Hamburg a draw with his goal after 77 minutes.
Schalke have lost just once in their past 13 games to improve to 55 points for second place - one point behind leaders Bayern Munich.
Hamburg had just a three-day break after advancing to the Europa League quarter-finals to move to 44 points for sixth place - one point behind Werder Bremen for the final European spot.
Kuranyi had the first chance of the game after 11 minutes but Hamburg goalkeeper Frank Rost fended the attempt for a corner.
Rost again proved better than Kuranyi in the 27th minute after Jefferson Farfan swiped at a ball from David Rozehnal and the former Germany striker was unable to beat the wily veteran one on one.
Hamburg went ahead five minutes before the break thanks to a superb volley by Van Nistelrooy who struck home the rebound of Piotr Trochowski's free-kick as Schalke goalkeeper Manuel Neuer could not collect the hard shot.
Things in the second half got a bit more hectic and Kuranyi finally beat Rost. Alexander Baumjohann's shot was deflected and Rozehnal's clearance attempt went to the far-right post where Kuranyi headed in the equaliser after 62 minutes.
Schalke jumped ahead just six minutes later following a twice-taken penalty.
Baumjohann was ruled to have been felled by Van Nistelrooy and Joris Mathijsen. Rakitic stepped up and beat Rost to the lower-left corner but two Schalke players entered the area too early.
Rakitic kept his nerves and beat Rost again from the spot - this time to the lower-right corner for a 2-1 lead after 68 minutes.
Schalke nearly double their lead six minutes later as Edu circled Rost and appeared to have room to score but Hamburg's Tomas Rincon cleared off the line.
The hosts equalised with 13 minutes left with Trochowski's cross from the left side made it across the entire mouth of the goal to the far-right post where Pitroipa poked home.
Schalke continued to push forward with Baumjohann hitting the crossbar from 22 yards in the 79th minute and Mathijsen clearing Kuranyi's header off the line two minutes later.