Everton have confirmed that full-back Seamus Coleman sustained a hamstring injury in the 2-2 friendly draw with Tranmere Rovers on Tuesday.
The Ireland international was a half-time substitute at Prenton Park but had to be withdrawn in the second period as a precaution.
Roberto Martinez says the club's medical team do not know how serious the injury is as yet but confirmed Coleman will not travel to Thailand for the friendly with Leicester in Bangkok on Sunday.
It certainly makes sense to play it safe at this stage of pre-season. The long-haul journey involved in getting to Thailand will also only exacerbate things, meaning a few days of assessment is the definitely the right call.
Speaking to the club's website, Martinez said:
"We assessed Seamus’ injury this morning.
"He will miss the Thailand trip to give proper consideration to his injury, for proper treatment and to remove any chance of aggravating that feeling that he had.
"We don’t really know the extent of the injury yet but it is sometimes a little bit of a setback that comes with pre-season preparation and getting a lot of volume into the bodies. Hopefully it is going to be just a minor setback."
The Spaniard also confirmed that Arouna Kone and Bryan Oviedo will stay behind over the weekend to continue their recoveries.
Kone has not played since October due to a knee injury while Oviedo suffered a horrific broken leg against Stevenage in January.
Both are back training but are unlikely to play a full role in pre-season, with Martinez previously estimating a September return for both players.
One player who is back in action though is Darron Gibson. The midfielder has been out since October with a knee injury of his own but played the second 45 minutes against Tranmere.
The boss is obviously pleased to have the Ireland man back as he will create much needed competition in the Everton midfield.
"Darron looks really strong. It's been very frustrating for him to spend such a long time away from the football pitch.
"But when you see him using that technical ability he has and the quality he brings to the side, he is like a fresh player coming back to us.
"We need to make sure we give him the right amount of work now and I think we'll enjoy seeing Darron Gibson's football this season."