The Giallorossi manager included the 21-year-old playmaker in his squad for their season opener against Livorno but is aware a huge bid would be hard for the club to turn down
As Goal revealed on Tuesday, Spurs held talks with Roma director Walter Sabatini in London over a €35 million (£30m) move for the 21-year-old, and negotiations are believed to be at an advanced stage.
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"Every coach would love to have a player who scores 15 goals per season and who is a regular in the Argentine national team,” Garcia told reporters.
"Erik is in the squad, exactly like the other 22 players. I can't do anything about the transfer market, so I am concentrated on tomorrow's game to start with a win.
"I have faith in my club because this will be a strong Roma, which is important for the fans and for all of us. I trust the club will give me options, so if someone leaves he'll be replaced by someone of the same level."
Garcia also hinted that if the fee was large enough it would be difficult for Roma to reject a bid for Lamela, regardless of how soon the season begins.
He added: "There are two aspects to be considered: sporting and financial. At times the financial aspect comes first.
“I always consider the transfer market to be the worst time for a coach and the fact our season begins before the session has closed is irritating.
"We are working along with the directors and I trust they will give me a competitive squad."