By ESPNSTAR.com staff
The Giallorossi were on track for victory when Erik Lamela opened the scoring eight minutes in, but Lazio soon gained the ascendancy in the wet conditions at the Stadio Olimpico, and overturned the deficit thanks to goals from Antonio Candreva and Miroslav Klose.
Roma's hopes then took a big blow when talismanic midfielder Daniele De Rossi got sent off just before the break, which Lazio capitalised on shortly after the restart when Stefano Mauri made it 3-1.
Mauri then turned from hero to villain when he too received his marching orders, and although Miralem Pjanic pulled one back from a freekick, the Biancocelesti ultimately held on for all three points.
Speaking after the game, Zeman admitted the defeat was hard to accept but paid tribute to his side's never-say-die attitude.
"Roma fans always feel close to their team and have dealt with defeats in the past," he said on the club's official website. "Including in the derby.
"Of course these things burn more when they happen against Lazio, but I don't think anyone's going to change their team because of it.
"We actually played our game in the first 20 minutes while the conditions still allowed us to do so. Then unfortunately, with all the rain that came down, my team weren't able to play as they know how.
"It's always bad to lose the derby but I don't think my lads ever gave up, and they nearly equalised through Marquinhos in the 93rd minute. The goals we conceded were more down to bad luck than the ability of our opponents, who were still good however."
Sunday's defeat leaves the Giallorossi 7th on the table, 14 points behind leaders Juventus, but Zeman insists their season is far from over, citing the example of Inter Milan, who recovered from a slow start and are now second.
"The season isn't over yet," he added. "The same things were said about Inter after two games but now they're in second.
"We still have the possibility to play for them [the top spots] and move forward with our style of football. So far we've lost games because of silly mistakes or bad luck."
The 65-year-old also admitted De Rossi may have left the occasion get the better of him, after the Italy international left the referee with no choice but to dismiss him when he hit Mauri in the face.
"I'm sorry about what he [De Rossi] did," Zeman said. "We studied how to face this game for two days.
"We shouldn't have given the referee things like this to judge us on, but the derby is the derby and when you feel too charged up for it you pay."
Roma will be looking to get back to winning ways next Monday when they entertain Torino.