The right-back has made just one appearance for the Reds so far this pre-season, and after working his way back from a hamstring injury, is now struggling with a back problem.
After the Reds’ penalty shootout loss to Atletico Madrid in the Audi Cup on Wednesday, the German discussed his options at right-back.
And in doing so, Klopp conceded that it is “pretty much impossible” that Clyne will make his return at Vicarage Road.
“He’s on the way back but he’s had no pre-season so far so, for him, it will not only be tight for Watford, it’s pretty much impossible,” he told reporters at the Allianz Arena.
“All of them played the position and now we have to bring them through the next one-and-a-half weeks and hopefully Clyney can come back after this. We have to make a decision.”
Gomez began Wednesday night’s clash with Atletico at centre-back, before shifting to right-back on the introduction of Joel Matip at half-time.
The 20-year-old looked markedly more comfortable in the latter role, though he tired as the game wore on, eventually making way for Alexander-Arnold on 74 minutes.
Gomez’s form throughout pre-season has been a source of encouragement for the Reds, with the youngster looking to put his injury issues behind him after a long layoff in 2015.
And Klopp believes his successful recovery, and his versatility, could make him a useful option in 2017/18.
“For Joe, after the long injury he came back in the middle of the season [in 2016/17] and was not as quick as he was before,” he continued.
“But he got it all back and he’s in really good shape and so it’s very important for us that we could bring him in both positions.”
At this stage, it seems most likely that Gomez will be Klopp’s starting right-back against the Hornets, given his more well-rounded quality compared to Alexander-Arnold.
Flanagan has been used sporadically in recent pre-season games, suggesting the 24-year-old is lowest down the pecking order as the season nears its beginning.