SHANGHAI, China -- Mercedes set the fastest practice times again at the Chinese Grand Prix on Friday, though rivals Ferrari and Red Bull may have closed the gap somewhat on Formula One's runaway leader.
Mercedes' Lewis Hamilton, winner of the past two F1 races, was quickest around the Shanghai International Circuit in the afternoon session after a suspension problem limited him to only nine laps in the morning session.
Ferrari's Fernando Alonso, however, was just 0.141 seconds behind Hamilton under the watch of new team principal Marco Mattiacci, who arrived in Shanghai to take charge following Stefano Domenicali's abrupt departure this week.
Alonso also set the quickest time during the morning practice.
Hamilton was delayed in the garage for a half hour in the afternoon session while his crew tried to resolve the suspension trouble.
"It's great to be still up front even though we have those issues," he said. "But, still, you want to get the car ready, you want to get the long runs feeling a little better, so there's some work to do."
Teammate Nico Rosberg had the third-fastest practice time, about 0.4 seconds behind Hamilton. He said Mercedes still expects to win the race on Sunday, even if its rivals performed well in practice.
"We're still looking pretty decent at the moment," he said. "The competitors are pushing -- today, Ferrari was very close."
Mercedes has dominated the season, with Hamilton winning in Bahrain and Malaysia and Rosberg in Australia. Only an engine problem on Hamilton's car in the opening race in Melbourne prevented three successive one-two finishes.
But Alonso, the defending Chinese GP champion, kept pace with them in the cool conditions of Shanghai, indicating his struggling team may just emerge as a challenger on Sunday.
Ferrari has lagged behind Mercedes following the series' switch to V6 turbo hybrid engines, and new fuel-saving regulations. The slow start prompted Ferrari to part ways with Domenicali after six years, replacing him with Mattiacci, formerly president of Ferrari North America.
Red Bull also kept up the pace on Friday, with Daniel Ricciardo and Sebastian Vettel finishing fourth and fifth, respectively.
Ricciardo said, however, he believes Mercedes may have been holding back during practice.
"We have to see where they are tomorrow. The gap seems a bit too close for now," he said. "I would like to say we've caught up but they've got a bit more in there."
He was pleased with Red Bull's improvement since Bahrain, where both drivers finished off the podium.
"We're making small improvements," Ricciardo said. "I mean, the gap is a big one so it's not going to come over one race, but we've crept up a little bit more."
Felipe Massa of Williams was sixth fastest in afternoon practice, followed by Ferrari's Kimi Raikkonen, who missed the morning session due to a mechanical problem.
McLaren's Jenson Button, Lotus' Romain Grosjean and Toro Rosso's Daniil Kvyat rounded out the top 10.
Smog hampered visibility at the circuit on Thursday, but conditions were relatively clear for Friday's practice. Rain and cool temperatures were forecast for Saturday's qualifying session.