Philipp Oettl was fastest on the opening day of Moto3 Czech Grand Prix practice, while championship leader Jorge Martin suffered a wrist injury.
Gresini's Martin made a play for the top of the timesheets in the closing stages of FP1, taking over with a 2:09.630s, before improving to a 2:09.533s.
A third effort of 2:09.533s followed, but a heavy crash at the Scwhantz corner saw him suffer a left wrist fracture, and his ruled the championship leader out of the remainder of the weekend.
Teammate Fabio Di Giannantonio was the very early pacesetter in FP1 with a 2:10.354s, while it was Philipp Oettl who ended the session fastest of all with a 2:09.194s.
Martin remained second despite his crash, with John McPhee making a late charge for third ahead of Aron Canet and Jakub Kornfeil.
Di Giannantonio once again came out of the blocks with the bencmark in the opening stages of FP2, guiding his Honda to a 2:09.698s, which was beaten some 10 minutes later by RBA KTM's Gabriel Rodrigo.
Rodrigo fired in a 2:09.580s to seize control of the timesheets, cementing his position with 11 minutes remaining with a lap 0.070 seconds quicker.
With three minutes remaining, his RBA teammate Kazuki Masaki made a surprise jump to the top of the order with a 2:09.288s, which remained untouched as FP2 came to a close.
However, Oettl's 2:09.194s from the morning session kept him top of the combined standings, wit Masaki's FP2 best moving him into second ahead of Aron Canet, who was second fastest in FP2.
Fourth overall and third in FP2 was Sky VR46 rider Nicolo Bulega, who managed the sixth-best time in the morning session. The top five on combined times was completed by Lorenzo Dalla Porta.
Di Giannantonio ended the day sixth overall from Adam Norrodin, while Martin remained eighth despite being absent from FP2. The top 10 was rounded out by Rodrigo and McPhee, who was mystifyingly off the pace in 18th in FP2.
Niccolo Antonelli, 17th in FP2, was the only other faller on Friday. The Italian suffered a nasty highside exiting Turn 13 early in FP2, but escaped the tumble without injury.
