ANAHEIM -- After an appeal, Héctor Santiago’s 10-game suspension for using a grip-enhancing substance has been upheld by Major League Baseball, a source confirmed to MLB.com on Thursday.

Santiago will begin serving his suspension on Friday, when the Mariners open the second half of the regular season against the Angels. He will be eligible to return on Tuesday, July 27, against the Astros.

In the interim, Seattle will not be able to fill Santiago’s 26-man roster spot, which will not only put them down an extra pitcher, it’ll also remove the likeliest fill-in for Justus Sheffield’s rotation spot as the lefty recovers from oblique and forearm injuries. The next turn for Sheffield, who was placed on the 10-day injured list on July 7 and is expected to be out a prolonged period, would’ve been on Tuesday against the Rockies.

Santiago became the first -- and remains the only -- player to be ejected for using a sticky substance since the league announced on June 15 that it was going to more aggressively crack down on grip-enhancing agents. Santiago was removed from a June 27 game against the White Sox, received the suspension two days later then had his appeal heard last week in Seattle.

The 32-year-old left-hander has maintained that the substance in question was the mixture of his sweat and rosin, which is legal. He was told by crew chief Tom Hallion upon being ejected that the sanction was due to the moisture being on the interior of his glove, which was confiscated and later examined during the appeal.

The glove has not been returned to Santiago, and his backup glove was deemed too black, so he’s purchased a third glove that is bright blue.

Santiago has been a solid contributor out of the Mariners’ bullpen, mostly for his versatility. He’s been able to start in a pinch, come in during a leverage moment, pitch on back-to-back days and more. The 10-year big leaguer has a 3.33 ERA in 24 1/3 innings over 12 appearances after signing with the Mariners as a depth piece for Triple-A Tacoma five days before its regular-season opener on May 6.