MONTE CARLO, Monaco - Formula 1 World champion Sebastian Vettel has likened Nico Rosberg's Monaco GP-winning Mercedes to a silver bus.Red Bull's championship leader came second behind Rosberg in a race that ran like a procession on Monaco's streets in the early stages as drivers sought to conserve their tyres for one-stop strategies.Vettel, who started behind Rosberg's Mercedes and 2008 champion Lewis Hamilton which had the front row, said: "I was a bit surprised by the slow pace in the opening laps. "Usually you expect two silver arrows in front of you but there were two buses going for a cruise - at least in the first couple of laps."The strategy was clear and they did a very good job. They were going quite slow and trying to make the one-stop happen. Fair play, they were in the lead - around here it's very tricky to pass."SLOW GOWebber's team mate Mark Webber agreed that the pace "wasn't electric", the race "not super-exciting", until crashes wrecked the pre-race planning by forcing the pace car into action and halting the race for 25 minutes.Most drivers re-started the race on supersofts and made them last for the remaining 32 laps.The quick-wearing Pirelli tyres have been a bone of contention so far in 2013; the previous race in Spain was won by Ferrari's Fernando Alonso after a four-stop strategy that proved the norm.It's extremely difficult to overtake at Monaco, though the tight and twisty track is kinder to tyres. There's a premium on pitting as few times as possible to avoid losing position.Rosberg, the first son of a Monaco winner to also win the glamour race, had been concerned about tyres from the moment he qualified on pole. He also started the previous two races on pole without winning as Mercedes failed to translate its one-lap speed into long-run performance. Stay with Wheels24 for the 2013 Formula 1 season – fresh reports every day.