Lopez believes he may have been tipping his pitches during his appearance Thursday, James Fegan of The Athletic reports.
Lopez was hit hard throughout his appearance, surrendering four extra-base hits in his three innings of work. He allowed a total of five earned runs, three of which came on back-to-back homers in the third frame. Lopez, who's competing for the final rotation spot with Carlos Rodon, pitched two perfect innings in his previous outing.